Ray Optics and Optical Instruments

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Q11. A ray of monochromatic light is passing through an equilateral prism $(ABC)$ as shown in the figure. The refracted ray $(QR)$ is parallel to its base $(BC)$ and the angle of incidence $(i)$ is $50^\circ$ . Then the angle of deviation $(\delta)$ is:

$40^\circ$
$45^\circ$
$55^\circ$
$35^\circ$

Explanation:

Hint:

δ_{m i n} = i + e - A

$\delta _{\mathrm{min}}=i+e-A$

Step: Find the angle of deviation.
The deviation in the prism is given by;
$\delta = i +e-A$
Where, $A = r_1 +r_2$ , since the path is symmetric ( $(r_1 = r_2)$ ) so, the angle of incidence is equal to angle of emergence i.e., $i = e = 50^{\circ}$
Therefore, the angle of deviation is given by;
$\Rightarrow \delta = 50^{\circ} +50^{\circ}-60^{\circ} = 40^{\circ}$
Hence, option (1) is the correct answer.

#592783

Exam: NEET – 2026

Q12. In a concave lens, a ray of light emanating from the object parallel to the principal axis of the lens, after refraction:

emerges parallel to the principal axis
appears to diverge from the first principal focus
passes through $2F,$ which is the radius of curvature of the lens
passes through the second principal focus

Exam: NEET – 2026

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