A student performed the experiment of glass slab and with different angles of incidence measured the angles of refraction and emergence in each case. He then recorded his observations as given in the table.

S.No.	Angle of incidence	Angle of refraction	Angle of emergence
A	$30°$	$25°$	$30°$
B	$40°$	$42°$	$40°$
C	$50°$	$50°$	$50°$
D	$60°$	$60°$	$62°$

The correct observation is :

Four students A, B, C, and D showed the following traces of the path of a ray of light passing through a rectangular glass slab. The trace most likely to be correct is that of student -

In an experiment on tracing the path of a ray of light through a rectangular glass slab, four students A, B, C, and D used the following values of the angle of incidence and the distance between the feet of the two pins (fixed on the incident rays) :

(A) $30°, 45°, 60°$ and $1 \mathrm{cm}$

(B) $30°, 45°, 60°$ and $6 \mathrm{cm}$

(C) $20°, 50°, 80°$ and $10 \mathrm{cm}$

(D) $20°, 50°, 80°$ and $15 \mathrm{cm}$

Out of these, the best choice is that of the student:

A student while performing the experiment on tracing the path of a ray of light passing through a rectangular glass slab measured the three angles marked as ${\theta }_1, {\theta }_2 and {\theta }_3$in the figure.

His measurements could be correct if he were to find :

In the experiment on tracing the path of a ray of light  passing through a rectangular glass slab, the correct setting of the protractor (D), for measuring the angle of incidence$(\angle i)$, and the angle of emergence $(\angle e)$ correspond, respectively, to diagrams :

Four students A, B, C,and D selected the following items from the materials available in the science laboratory to perform an experiment to study the refraction of light through, a glass slab  :

(A) convex lens, glass slab, pins, drawing board, white paper, scale

(B) glass slab, pins, drawing board, scale, white paper, protractor

(C) glass slab, glass prism, candle, screen, pins, scale, drawing board, protractor

(D) concave mirror, pins, glass slab, protractor, white paper, drawing board

Correct choice of the items required is made by the student :

In an experiment to trace the path of a ray of light passing through a rectangular glass slab, four students measured the angles of incidence $\left(i\right)$ , angles of refraction $\left(r\right)$ and angles of emergence $\left(e\right)$ as shown in the diagrams :

The correct measurement is given in the diagram :

An experiment for tracing the path of ray of light through a glass slab was set up in the laboratory and ray diagram was drawn as shown here.

The teacher asked the students to identify the refracted ray. The correct answer is :