1
Question
A student suggested the following 'guidelines' to his friend for doing the experiment on tracing the path of a ray of light passing through a rectangular glass slab for three different angles of incidence:
A. Draw the 'outline' of the glass slab at three positions on the drawing sheet.
B. Draw 'normals' on the top side of these 'outlines' very near their left end.
C. Drawn the incident rays on the three 'outlines' in directions making angles of 30°, 45°, 60° with the normals drawn.
D. Fix two pins vertically on each of these incident rays at two points nearly 1 cm apart.
E. Look for the images of the 'heads' of these pins while fixing two pins from the other side, to get the refracted rays.
When he showed these 'guidelines' to his teacher, the teacher corrected and modified the 'guidelines' labelled as
(1) B, C, E
(2) B, D, E
(3) B, C, D
(4) C, D, E
A. Draw the 'outline' of the glass slab at three positions on the drawing sheet.
B. Draw 'normals' on the top side of these 'outlines' very near their left end.
C. Drawn the incident rays on the three 'outlines' in directions making angles of 30°, 45°, 60° with the normals drawn.
D. Fix two pins vertically on each of these incident rays at two points nearly 1 cm apart.
E. Look for the images of the 'heads' of these pins while fixing two pins from the other side, to get the refracted rays.
When he showed these 'guidelines' to his teacher, the teacher corrected and modified the 'guidelines' labelled as
(1) B, C, E
(2) B, D, E
(3) B, C, D
(4) C, D, E
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Solution
The guidelines which need to be modified are B, D, and E.
Because one should need to draw the 'normals' on the top side, very near their left end and also at the bottom, very near the right end. The distance between the pins should be 6 cm, not 1 cm to trace the path more accurately and also while fixing the other two pins on the other side, we need to look for the head of the pins such that they all be in a straight line, which helps us to get the path of the emergent rays not refracted rays.
Hence, the correct answer is option 2.
Because one should need to draw the 'normals' on the top side, very near their left end and also at the bottom, very near the right end. The distance between the pins should be 6 cm, not 1 cm to trace the path more accurately and also while fixing the other two pins on the other side, we need to look for the head of the pins such that they all be in a straight line, which helps us to get the path of the emergent rays not refracted rays.
Hence, the correct answer is option 2.
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