Abstract
A large scale study involving 1786 year 7–10 Korean students from three school districts in Seoul was undertaken to evaluate their understanding of basic optics concepts using a two‐tier multiple‐choice diagnostic instrument consisting of four pairs of items, each of which evaluated the same concept in two different contexts. The instrument, which proved to be reliable, helped identify several context‐dependent alternative conceptions that were held by about 25% of students. At the same time, students’ performance on the diagnostic test correlated with the location of the schools, students’ achievement in school science and their attitudes to science learning. However, students’ grade levels had limited influence on their understanding of basic concepts in optics as measured by the instrument.
Introduction
Students tend to hold particular idiosyncratic views about the scientific concepts that they bring with them to science lessons. These conceptions that students develop, referred to as student conceptions, are the result of several factors such as their sensory experiences and the influence of their peers, the media and previous instruction. Very often, the conceptions that students develop about the behaviour of matter tend to differ from the views that are held by the scientific community. It is likely that students are satisfied with their own conceptions as a result of viewing material that is presented by their teachers or textbooks ‘through the lenses of their preinstructional conceptions’ (Duit and Treagust Citation1995, 47).
The unique conceptions about natural phenomena and the properties of matter that are held by students are often resistant to instruction. One reason for this resistance to change is the tendency for these conceptions to become firmly entrenched in students’ minds as coherent but mistaken conceptual structures, especially when the conceptions are deeply rooted in students’ everyday life experiences. As a result, when a new concept does not make sense to students, they tend to adhere firmly to their own views. In the scientific area of light in particular, students find the subject confusing and difficult to understand and hence tend to acquire deep‐rooted inappropriate understandings that are resistant to change (Heywood Citation2005). An example is the speed of light, which is difficult for the human mind to perceive, yet light is represented in science teaching as being stationary (Galili and Hazon Citation2000). Also, to be able to explain optical phenomena requires the student to realise that the observer constitutes part of the optical system in addition to understanding the properties of light propagation (Langley, Ronen, and Eylon Citation1997).
Formal knowledge of basic geometric optics can be considered as consisting of four interrelated components: optical systems (configurations of light sources, mirrors, prisms and lenses), light propagation (rectilinear propagation, reflection and refraction), illumination patterns (shadows and images), and a systematic manner of linking the formal components using verbal, graphic and algebraic representations (Langley, Ronan, and Eylon Citation1997). The research that was undertaken in this study involved the use of verbal representations and diagrams relating to light propagation in air and the important role of eyesight in tracking light propagation.
Students’ understanding of light propagation concepts, eyesight and basic optical phenomena has been investigated in several studies over the past two decades or so. The different explanations that students gave for seeing luminous and non‐luminous material objects have been reported in at least two studies (Andersson and Karrqvist Citation1983; Langley, Ronen, and Eylon Citation1997). In their study, Langley, Ronan, and Eylon (Citation1997) found that students believed light from a luminous object was visible because light could travel in space, but there was no light propagation from a non‐luminous object. In the case of a lighted candle, for example, students believed that the candle was visible because light was leaving the flame and entering the eye. However, in the case of a flower, light that was present around the flower made the flower visible.
Another study involved, among other concepts, human and cat vision in daylight and at night (Fetherstonhaugh and Treagust Citation1992). Following an instructional module to engender conceptual change about the understanding of basic concepts in optics among 20 Year 8 students, 88% of students provided scientifically acceptable explanations for seeing in daylight and in the dark. Further, students’ alternative conceptions have been shown to not be very different from those of adults (Bengall, Goldberg, and Galili 1983), most likely because there were few opportunities for students to further develop their conceptions of basic optics in school, so students’ conceptions remain stable into adulthood.
In a study with 55 primary school preservice teachers on the optical phenomenon of perceiving an object, using six different diagrammatic representations, Heywood (Citation2005) investigated their explanations of how they see a tree. Analysis of their written explanations and interview transcripts revealed a variety of explanations for each of the diagrams. Although there was general consensus among all the students that a light source was necessary for the tree to be visible, the light was described variously as ‘shining on, illuminating, bouncing off, hitting and reflecting off the tree’ (Heywood Citation2005, 1456–7). Similarly, in a study involving primary school children, Shapiro (Citation1989) designed an instructional programme using basic light concepts like the need for light to be reflected off a house for it to be visible, to engender understanding of science concepts by guiding students’ personal orientation towards achieving a more positive experience in science learning.
Another study conducted with 238 Year 9 and 10 students investigated how they interpreted everyday phenomena involving light and human eyesight (Toh, Boo, and Woon, Citation1999). The study was based on a theoretical framework involving the three basic components: light, eyes and object. In order to demonstrate understanding of light propagation and eyesight, students needed to explain the interrelationships between all three components: more than 50% of both the Year 9 and 10 students possessed little or no understanding of light and eyesight concepts, being able to use only one or two of the three components in their explanations.
As students’ prior knowledge is known to influence what they learn during classroom instruction, it is essential that teachers are aware of their students’ knowledge including their preconceptions about a topic that is to be introduced (Driver et al. Citation1994; Tytler Citation2002.) A convenient way for teachers to identify the conceptions held by students that are not in agreement with scientific views involves the use of two‐tier multiple‐choice items as formative assessment tools. With knowledge of students’ conceptions, relevant strategies may be formulated that can challenge their understandings in order to help students develop more scientifically acceptable views of science concepts (Treagust Citation1995). Several of these two‐tier multiple‐choice items that have been developed are reported in the science education research literature (Treagust and Chandrasegaran Citation2007). An instrument consisting of 24 items that evaluate students’ understanding of light propagation concepts has been developed by the authors. Eight of these items from this instrument have been used in this study and are referred to in the methodology section.
In addition, several personal and demographic factors such as students’ unique environment, motivation, attitude and beliefs in science also have an influence on their conceptual understanding (Chu, Treagust, and Chandrasegaran Citation2008; Hammer Citation1994; Pintrich, Marx, and Boyle Citation1993). It is widely accepted that the motivational and attitudinal states of learners have an influence on students’ conceptual development. For these reason students’ attitudes, beliefs and extent of their motivation for learning science were explored, although only to a limited extent.
Purpose of study
This study involving basic optics concepts of light propagation and illumination patterns was conducted in order to investigate: (1) students’ general alternative conceptions; (2) students’ context‐dependent alternative conceptions; and (3) factors influencing students’ conceptual understanding. As shown in the review of related literature, while there have been a number of studies about students’ understanding of light, all have been conducted with small samples. No study has examined context‐dependent light concepts using two‐tier diagnostic items with a very large sample.
Methodology
The investigation was a large‐scale quantitative study involving 1786 Years 7–10 Korean students (Year 7, 410; Year 8, 458; Year 9, 367; Year 10, 551) from three school districts (near Seoul, North Seoul and South Seoul). In Korea, Years 7–9 are in middle school, Years 10–12 are in high school.
Data were collated using two instruments (the Light Propagation Diagnostic Instrument (LPDI) and the Science Attitude Questionnaire (SAQ)) that were administered to students from three middle schools and four high schools. The instruments were administered during normal curriculum time over a period of two weeks by the first author’s former students and colleagues who are science teachers. The cooperation of the class teachers in the various schools was sought prior to administering the instruments. Students were able to respond to the questionnaires because the content of the LPDI covered material that was included in the science curriculum. On average, students completed the questionnaires in 30 minutes.
Questionnaires
The LPDI was developed by the authors based on items used in previous studies (Fetherstonaugh and Treagust Citation1992; Langley, Ronen, and Eylon Citation1997; La Rosa et al. Citation1984), and consisted of eight two‐tier multiple‐choice items with a Cronbach alpha reliability of 0.65. Each of four pairs of items in the LPDI investigated students’ understanding of a particular concept in different contexts. The contexts of the items and the common concept associated with each pair are summarised below.
First item pair
Item 1 (light propagation during the day) and Item 2 (light propagation at night) involved the concept that ‘light travels in straight lines in all directions until it strikes an object’.
Second item pair
Item 3 (visibility of a non‐luminous object) and Item 4 (visibility of a luminous object) involved the concept that ‘light travels in straight lines to our eyes from both non‐luminous and luminous objects and is then focused on the retina’.
Third item pair
Item 5 (visibility of a lighted lamp above an obstruction) and Item 6 (illumination by a lighted lamp above an obstruction) involved the concept that ‘light travels in straight lines past an obstruction’.
Fourth item pair
Item 7 (vision of cats in the dark) and Item 8 (human vision in the dark) involved the concept that ‘an object is visible because light is reflected from the object to the eyes’.
An example of a pair of context‐dependent items (Items 3 and 4) is shown in Figure . The response to an item was considered to be correct if students answered both tiers of the item correctly. A correctly answered item was scored ‘1’ while an incorrect response was scored ‘0’. Hence, the total score ranged from 0 to 8.
Figure 1 Example of one pair of context‐dependent items.
The SAQ that was developed by the authors based on previous studies (Chu, Treagust, and Chandrasegaran Citation2008; Hammer Citation1994; Pintrich, Marx, and Boyle Citation1992) consisted of five items (see Table ) with an alpha Cronbach reliability of 0.84. The items in the SAQ were 10‐scale Likert‐type statements involving students’ attitude to science in everyday life, students’ preference for science and the ways students study physics. The attitude items were on a 10‐point scale ranging from ‘strongly disagree’ to ‘strongly agree’. The total score for the attitude items ranged from 5 to 50. Points 1–4 were considered as negative responses, Points 5–6 were considered as neutral responses and Points 7–10 were considered as positive responses. In addition, students’ demographic variables of gender, school year, school district and school science achievement scores were solicited.
The cross translation of the instruments between English and Korean and vice versa was done and verified with the assistance of two science educators from Korea and Australia. The two instruments were first pilot‐tested by administering to 30 Korean students in Years 7 to 10 from schools in Seoul in order to ensure that they understood the scientific terms and language that were used.
Data analysis
The percentage of correct answers/positive responses, the means of the LPDI and SAQ, and correlations between the LPDI and the SAQ were analysed using the SPSS software (Version 14). Standardised T scores (Rust and Golombok Citation1999) of the dependent variables (students’ understanding of basic optics concepts and their attitude to science), computed using the formula (50 ± 10 x z score), were used in a MANOVA analysis to find out how these variables were affected by the four independent variables (gender, school year, school science achievement scores and school district). In addition, correlations between students’ attitude and conceptual understanding were determined using the Pearson correlation coefficient.
Discussion of results
Item analysis of the LPDI
Students’ correct answers to paired items
The paired Items 1 and 2, 3 and 4, 5 and 6, and 7 and 8 each involved the same science concept in different contexts. For each pair of items, the percentage of students who correctly answered both items was lower than the scores for each of the items (see Table ). This trend indicated limited ability of the students to apply the same concepts in different contexts. For Items 3 and 4 and Items 7 and 8 in particular, the percentage of correct responses to both items was much lower than that for each of the individual items, indicating even greater difficulty experienced by students in applying particular concepts in different contexts.
Table 1. Number of students with correct answers (% in parentheses).
Students’ general alternative conceptions
For the purpose of this study, scientifically incorrect responses that were held by at least 10% of the students were considered to be alternative conceptions. The alternative conceptions that were identified in the study are summarised in Table . In addition, the table provides the percentage of each of these alternative conceptions that were displayed by students in the separate year levels. These alternative conceptions have been classified into five categories, namely: (1) light travels in a preferential way toward an object; (2) light stays around an object; (3) we see an object because it is there; (4) light from a lamp is visible at all points above an obstruction; and (5) objects can be seen without considering our eyes having to focus the rays on the retina.
Table 2. General alternative conceptions determined from the administration of the light propagation diagnostic instrument (LPDI).
As indicated in Table , all but one of these alternative conceptions were displayed by students from all school years; only Year 8 students indicated that an object was visible because it was located within a person’s region of vision.
Among the alternative conceptions referred to in Table , several context‐dependent alternative conceptions were identified which was the primary purpose of the research.
Students’ context‐dependent alternative conceptions
The paired items were designed to use the same science concept in different contexts. Among the students’ general alternative conceptions in Table , there were alternative conceptions that could be found in only one of the items in each item pair, that is, only in one context and as a result are referred to as context‐dependent alternative conceptions. For example, several students who displayed understanding of light propagation at night did not indicate understanding of similar concepts in the day time context. Also, students indicated that they could see an object because it was there, but they had different reasons for illuminated objects (because the objects were located in their line of vision) and non‐illuminated objects (because merely bundles of rays were emitted). For non‐illuminated objects, students did not consider light propagation concepts while for illuminated objects students did not consider the light as entering the eyes. Students also indicated that cats have the ability to see objects in the dark and people are able to see an object in the dark after their eyes have adjusted to the darkness, without considering the principles of light propagation.
Among the alternative conceptions listed in Table , the context‐dependent alternative conceptions were investigated through a cross analysis of the responses to the paired items. The cross analysis results of responses to one pair (Items 3 and 4) are shown in Table . For example, 16–24% of students held the alternative conception A1 (that we are able to see an object because of bundles of rays from the object without considering our eyes having to focus the rays on the retina) in Item 4 (see Table ). This alternative conception (involving more than 10% of students) is a context‐dependent alternative conception as it was not identified in Item 3 (see Table ). Instead, the alternative conception ‘Light is only present around the flower’ (response D3) was held by 21–29% of all students, while 10% of students in Year 7 and Year 9 selected the wrong light propagation diagram even though they were able to choose the correct response in the first tier (‘Light is shown emanating from the object and being received by the eye’). Also, 14–33% of students chose an acceptable scientific conception A4 (‘Light is shown emanating from the object and being received by the eye’) in Item 3.
Table 3. Distribution of responses (selected by more than 10% of students) in Item 3 when students held the alternative conception ‘bundle of rays from the object without considering our eye focusing the rays on the retina (A1)’ in Item 4.
In the context of an illuminated object, students tended to focus only on the words, ‘bundle of rays from the object’ because light propagation is described in textbooks using this terminology. Especially when students have to deal with the image that is formed through the lens by a bulb and a candle, textbooks describe the image using bundle of rays from the object without reference to the role of the retina in facilitating vision.
Even among students who chose an acceptable scientific conception in the context of a non‐illuminated object in Item 3, 19–27% of students suggested that ‘bundle of rays from the object’ enabled the boy to see the candle in Item 4. They were not able to use the same scientific conception that they held in Item 3 about the flower in the context of an illuminated object in Item 4.
Based on the cross analyses of students’ responses to the four paired items in the different contexts, a list of context‐dependent alternative conceptions were identified and are summarised in Table . Only alternative conceptions in Table that were held by at the least 10% of the students were identified. Using cross analysis of students’ responses, three alternative conceptions from Table (Nos. 3, 9 and 10) were identified that appeared in one item of a pair but did not recur in the other item. These three alternative conceptions (summarised in Table ) are context‐dependent alternative conceptions. An example of the cross analysis results is provided in Table for the students who held the alternative conception that an object was visible because of bundles of rays emanating from the object without considering the need to focus the rays on the retina in Item 4, but did not display this alternative conception in Item 3.
Table 4. The percentage of students’ context‐dependent alternative conceptions identified from the paired items in the different contexts.
Students in Years 8 and 9 indicated that light stays on the light bulb during the day (Item 1: A2, 35–46%; see Table ). Among these students 20–41% selected the correct answer that light travels in all directions from the bulb until it hits something (D1), and 37–40% suggested that light rays travel in a preferential way towards an object (D5) in Item 1. No students retained the same conceptions in Item 2.
Students from all school years had difficulty understanding that our eyes have to focus the light rays on the retina. They held alternative conceptions suggesting that we are able to see an object because of bundles of rays radiating from the illuminated object (Item 4: A1, 16–23%). Even though students understood the necessity for light to be reflected from an object to the eyes in order for the object to be visible, they believed that cats possess the special ability to see in complete darkness (Item 7: C3, 26–35%; see Table ).
Cross analysis of four other alternative conceptions in Table (Nos. 4, 5, 6 and 11) indicated that these students’ alternative conceptions were not context‐dependent; 30–40% of students who held these alternative conceptions in one item retained these conceptions in the other item of the item pair. For example, when students held the alternative conception about the light propagation diagram in the context of an illuminated object in Item 4 (D4: 11–16%), 35–41% retained the same alternative conception in Item 3.
Item analysis of the SAQ
Students’ attitudes to science were evaluated based on their school learning experiences as well as the influence of the media. The percentage of students’ positive responses in the science attitude questionnaire (SAQ) is presented in Table . Analysis of the SAQ responses showed that the percentage of students who liked to watch TV programmes or read about science related documents (Items 1 and 2 in Table ) ranged from 20% to 34%. Also, only 29% to 40% of students indicated that they liked learning science which could account for their relatively low interest in learning about science through the media. However, a higher proportion (38–56%) indicated that they liked school science lessons and science experiments. This discrepancy in interest may indicate that school science lessons with their practical activities were more engaging for the students. As for interest in learning physics, in particular, a relatively small number of students liked the subject most among all science subjects (15–25%). Overall, students displayed less positive attitudes toward science as they progressed to higher year levels.
Table 5. Number of students’ positive responses in the Science Attitude Questionnaire (SAQ) (% in parentheses).
Analysis of the variables affecting students’ basic conceptions and attitude to science and correlations between LPDI and SAQ
The correlations between students’ conceptual understanding in basic optics and attitude to science for each year level were investigated using the corresponding standardised mean scores. The correlations increased slightly across school years (Year 7: r = 0.26; Year 8: r = 0.27; Year 9: r = 0.32; Year 10: r = 0.33: Overall: r = 0.29).
To investigate the factors that influenced students’ conceptual understanding in basic optics and attitude to science, the variables gender, school year, school science achievement scores and school district were considered. All variables had an influence on their attitude to science. All variables, except school year, influenced students’ basic optics conceptions, with school science achievement scores being most effective (see Figure ). Male students displayed better conceptual understanding and more positive attitude to science than girls (conceptual understanding – Male: 50.6 ± 10.1, Female: 48.9 ± 9.8, F = 11.3, Eta2 = 0.01; attitude – Male: 51.5 ± 9.9, Female: 46.9 ± 9.6, F = 83.6, Eta2 = 0.05). Students who attained high science achievement displayed better conceptual understanding and attitude to science (Table ). Also, students from North Seoul district displayed the least positive attitude to science and possessed the weakest conceptual understanding (conceptual understanding – North Seoul: 47.7 ± 9.1, South Seoul: 51.73 ± 10.7, Near Seoul: 50.6 ± 9.8, F = 23.7, Eta2 = 0.03; attitude – North Seoul: 48.2 ± 9.9, South Seoul: 51.6 ± 10.3, Near Seoul: 50.2 ± 9.6, F = 15.7, Eta2 = 0.02). This trend is not surprising because the students from North Seoul who were involved in this study were the least interested in studying physics and were from lower socioeconomic backgrounds.
Figure 2 The variables affecting students’ basic optics conceptions and attitude to science (results obtained using a MANOVA).
Table 6. Comparing means of conceptual understanding (LPDI) and attitude to science (SAQ) depending on school science achievement scores (N=1777).
Conclusion and educational importance of the study
Several conclusions may be drawn from this study. Firstly, students from all years in these Korean schools displayed similar alternative conceptions as those that are reported in the research literature. Among these alternative conceptions were the understandings that: (1) light travels in a preferential way towards an object; (2) light stays around an object; (3) we see an object because it is there; (4) light from a lamp is visible at all points above an obstruction; and (5) objects can be seen without considering our eyes having to focus the rays on the retina. The fact that these alternative conceptions permeated through all school years is not surprising because optics is taught only in middle school in Year 8 in the Korean science curriculum and so it is likely that students have forgotten what they had previously learned as they progressed to higher year levels of education. Furthermore, the limited reference in the curriculum to students’ everyday life experiences with light propagation may have contributed to their alternative understanding of the concepts that were involved.
Secondly, several of the students’ alternative conceptions were context‐dependent; many students could not apply their conceptions in basic optics in different contexts. For example, 26–35% of students in Years 7–10 held the conception that cats were able to see in the dark whereas humans were not, without considering the need for light to be reflected off an object for it to be visible. Also, 35–46% of Years 8 and 9 students indicated that light from a bulb was visible only at night but stayed around the bulb when it was switched on in the daytime. Thirdly, students’ attitude to science was highly correlated with their understanding of basic optics concepts. Correlations between these factors increased slightly (from r = 0.26 to r = 0.33) from Year 7 to Year 10, with an overall correlation of r = 0.29.
Fourthly, the factors gender, school district and school science achievement scores had a significant correlation with students’ understanding of basic optics concepts, with the last factor having the most significant effect. School year, however, did not influence students’ understanding. At the same time, all four factors were significantly correlated with students’ attitude to science, with gender and school science achievement scores having the greatest influence. Fifthly, conceptual understanding and attitude to science were found to be strongly correlated with school science achievement scores in this research, as evidenced by a significant increase in the mean standardised scores for conceptual understanding and attitude to science as students’ school science achievement scores increased.
This study also has several pedagogical implications and is unique in the sense that apart from elucidating information about students’ alternative conceptions about basic optics concepts, the emphasis has been on evaluating students’ understanding in contextual settings from a very large student population. From the point of view of classroom teaching and learning, the two‐tier diagnostic test in basic optics has proven to be a valuable diagnostic assessment tool that can help teachers to diagnose their students’ preconceptions before commencing their lessons. Having identified typical alternative conceptions in basic optics using this diagnostic test, teachers can take these student’s conceptions into account in their teaching plans with a view to improving students’ understandings in this area.
In addition, this study has shown that a large proportion of students involved did not develop the basic concepts in optics that they had learned in earlier years. A recurring issue here is not to teach concepts in isolation but to progressively build upon these concepts in higher grade levels so that students will be able to better understand these concepts in everyday contexts. Finally, students’ attitude towards the learning of physics could be further improved by teachers making use of examples that are relevant to their everyday lives as in the examples of the items that were used in this study.
Acknowledgement
This research was funded by a grant from the Korean Research Foundation (KRF‐B00035) in 2006 for the first author’s work as a postdoctoral researcher with Professor David Treagust at Curtin University of Technology in Australia.
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