Overview of sub-study 1 - Improving students' learning about optics at university

Sub-study 1 focused on students’ learning of the electromagnet-ic nature of light. More precisely, we investigated students’ con-ceptions of the electric and magnetic fields and their interrela-tions after they had completed university courses in electro-magnetism and optics. Previous studies had identified various difficulties encountered by students in using the concept of field in their reasoning (Furiò & Guisasola, 1998; Törnkvist, Pettersson, & Tranströmer, 1993). In addition, students were of-ten shown to be unable to recognize the symmetric interrela-tions of the electric and magnetic fields (Guisasola, Almudi, &

Zubimendi, 2004; Ambrose et al., 1999; Bango & Eylon, 1997).

These findings suggested that a field-based description of light may be difficult for students to grasp, since it requires an under-standing of the basic assumptions of the field concept – e.g., the field exists in every point of space – and the interrelationships of the electric and magnetic fields.

In sub-study 1 the students’ conceptions of the electric and magnetic fields and their interrelations were investigated in dif-ferent contexts. The contexts chosen were a charge, a charging capacitor, an electromagnetic induction, and an electromagnetic plane wave. These contexts were chosen since the meaning of a field concept grows from the model of the interaction of the charges into a description of light. Thus, using these contexts, we were able to obtain an extensive description of students’

conceptions of the electric and magnetic fields and their interre-lations. This description, in turn, was supposed to provide in-formation on students’ prerequisites for understanding the elec-tromagnetic nature of light. In addition, these contexts seemed to create a useful base for the development of instruction that would aim at improving students’ understanding of the field concept and of the electromagnetic nature of light.

With the aid of the chi-square distribution table, the value of 𝜒𝜒² was converted to a 𝑝𝑝-value. If the 𝑝𝑝 value was greater than 0.05, then the students’ response distributions obtained in consecu-tive years did not differ significantly. Hence it was considered appropriate to merge the data sets collected in consecutive years into one.

In addition to the chi-square test for homogeneity, the McNemar test (Sheskin, 2003) was used in sub-study 2 to indicate the impact of the tutorial tasks on students’ learning. More pre-cisely, the test was used to discover whether the improvements in students’ responses were statistically significant or not. For the test, the students’ knowledge was evaluated before (pre-responses) and after (post-(pre-responses) they had performed the tutorial tasks. These responses were categorized as correct or in-correct responses. The frequencies of these categories were cross-tabulated, as shown in Table 4.1. This Table took into ac-count only those students’ who had provided both pre- and post-responses.

Table 4.1. Frequencies organized to conduct the McNemar test

corrects post-responses incorrect post-responses

incorrect pre-responses 𝑎𝑎 𝑏𝑏

correct pre-responses 𝑐𝑐 𝑑𝑑

The value of the 𝜒𝜒² test variable was determined with the aid of the following equation:

𝜒𝜒²=(𝑑𝑑 − 𝑎𝑎)²

(𝑑𝑑 + 𝑎𝑎) . (4.3)

The value of the test variable was converted to 𝑝𝑝-values with the aid of a chi-square distribution table. If the 𝑝𝑝-value was less than 0.05, the improvement was considered to be statistically signifi-cant.

5 Overview of sub-study 1

Zubimendi, 2004; Ambrose et al., 1999; Bango & Eylon, 1997).

5.1 SURVEY DESIGN AND DATA-GATHERING

In sub-study 1 data was gathered with the aid of a cross-sectional survey (Cresswell, 2009). It served as a straightforward method of indicating what students had learnt during their earlier uni-versity studies that had focused on electromagnetism and optics.

The survey was implemented in a paper-and-pencil format con-sisting of four tasks, each covering a single context that was de-signed to be addressed in sub-study 1. The tasks were based on earlier studies (Ambrose et al., 1999; Eylon & Ganiel, 1990) and upper-secondary and introductory level textbooks. (Hatakka, Saari, Sirviö, Viiri, & Yrjänäinen, 2006; Knight, 2008a). The tasks are presented in article I.

The survey was conducted at the start of the Autumn semes-ter in 2008. The relevant background courses in electromag-netism and optics had ended more than 6 months before the da-ta was gathered. The dada-ta-gathering was implemented during a 45-minute lecture period. It permitted us to ensure that the stu-dents responded without resorting to external information sources such as textbooks or the internet. A total of 33 students responded to the survey. They were not informed in advance about the testing so as to ensure that their responses would re-flect what they had learnt from their previous studies of elec-tromagnetism and optics. All of the participants had completed the course in electromagnetism at university but not the course in optics. However, dividing the students into sub-groups ac-cording to their background studies would have provided no essential additional information. Thus, a total of 33 students were treated as a single group.

Recognizable patterns of students’ responses were catego-rized into content-specific categories reflecting students’ factual and conceptual knowledge concerning the electric and magnetic fields and their interrelationships. The frequencies of these cate-gories were calculated, and the catecate-gories and frequencies were presented in Tables. Finally, the results obtained were collated by holding a discussion of the possible origins of the students’

incorrect conceptions and of how they could be tackled with the aid of instruction in electromagnetism and optics.

5.2 MAIN RESULTS AND DISCUSSION

The results of sub-study 1 demonstrated that students held var-ious incorrect conceptions about the interrelationships of electric and magnetic fields. In the context of a charge, 15% of the stu-dents suggested that a magnetic field only exists around a charge that moves uniformly (constant speed to a certain direc-tion). In the contexts of a charging capacitor and of electromag-netic induction, approximately 30% of the students were unable to recognize the presence of an induced magnetic field or elec-tric field. And finally, in the context of an electromagnetic plane wave, 70% of the students demonstrated that they held a con-ception according to which the electric and magnetic fields are independent of each other.

The students’ incorrect conceptions reflected their lack of factual and conceptual knowledge about fields and their interac-tion. More precisely, many students were unable to recognize that a changing electric field creates a magnetic field, and vice versa. Due to their lack of these crucial pieces of knowledge, stu-dents demonstrated that they had difficulty in understanding the interrelationships of electric and magnetic fields. Especially in the context of the electromagnetic plane wave, a large propor-tion of the students (70%) incorrectly treated these fields as in-dependent entities. This indicated that the field-based descrip-tion of light is difficult for students to grasp. This, in turn, sug-gested that to improve students’ learning about the electromag-netic nature of light, more attention should be paid to teaching the interrelationships of the electric and magnetic fields. This was in fact the original scope of the present study, which was changed due to reasons explained in section 1.3.

5.1 SURVEY DESIGN AND DATA-GATHERING

incorrect conceptions and of how they could be tackled with the aid of instruction in electromagnetism and optics.

5.2 MAIN RESULTS AND DISCUSSION

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