Question

The teacher asked a student to describe the steps of the experiment of tracing path of light ray through a rectangular prism. He gave following statements. Which one of the following is not appropriate?
A) Take white sheet and pin up it on drawing board.
B) Trace the boundaries of given prism on the board and draw the normal.
C) Draw an angle of incidence 40
D) Pinup two pins one on left side and the other on right of prism along the line of angle of incidence.

Answer 1

Procedures-

1) Fix a sheet of a white paper on drawing board using drawing pins

2) Place a glass prism on it in such a way that it rests on its triangular base . Trace the outline of prism using pencil

3) Draw a straight line PE inclined to AB and fix two pins at point P and W on PE

4) Look for the images of pins and fix pins R and S on the straight line made from the images of P And Q

5) Remove the pins and prism

6) Line PE meets boundary of prism at point E and similarly join and produce R and S such that these lines meet the boundary of E and F .
join E and F

7)draw perpendiculars to the refracting surface AB and AC of the prism at points E and F respectively
8) Mark an angle of incidence <i, angle of emergence <e , angle of refraction <r

thus it does not include to make a angle if incidence fixed at 40°

therefore the correct option is C

hope helped.