Q: A microscope has an objective of focal length 2 cm , eyepiece of focal length 4 cm and the tube length of 40 cm . If the distance of distinct vision of eye is 25 cm , the magnification in the microsco

array ll f _0=2 ~cm & f _e=4 ~cm \\ ~L =40 ~cm & D =25 ~cm array In the condition of normal adjustment. aligned m & = L f _0 D f _e \\ & = 40 2 25 4 \\ & =125 aligned

Q: A light ray enters through a right angled prism at point P with the angle of incidence 30^ as shown in figure. It travels through the prism parallel to its base B C and emerges along the face A C. The

In prism, r_1+c=A gathered r_1=90^ -c (1)\\ c= 1 c= ^2-1 gathered Apply Snell's law, on incidence surface aligned 1 30^ = (r_1 ) 1 1 2 & = (90^ -c ) \\ 1 2 & = ^2-1 aligned On squaring 1 4 = ^2-1 ^2= 5 4 = 5 2

Question 1

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^ . Then the

Accepted Answer

For an equilateral prism, the angle of the prism is A = 60^ . It is given that the refracted ray inside the prism is parallel to its base. This implies that the prism is in the position of minimum deviation. In the position of minimum deviation, the angle of emergence e is equal to the angle of incidence i. Given i = 50^ , we have e = 50^ . The angle of deviation is given by the relation: = i + e - A Substituting the values, we get: = 50^ + 50^ - 60^ = 100^ - 60^ = 40^ Answer: 40^

Question 2

The lens combination as shown in the figure, consists of two lenses, L_1 and L_2, of the focal lengths +10 cm and -10 cm, respectively. The position of the image formed is :

Accepted Answer

For the first lens L_1 (convex lens): Object distance, u_1 = -30 cm Focal length, f_1 = +10 cm Using the lens formula, 1 v_1 - 1 u_1 = 1 f_1 1 v_1 - 1 -30 = 1 10 1 v_1 + 1 30 = 1 10 1 v_1 = 1 10 - 1 30 = 3 - 1 30 = 2 30 = 1 15 v_1 = +15 cm The image I_1 formed by L_1 acts as a virtual object for the second lens L_2. For the second lens L_2 (concave lens): Distance between the lenses, d = 3 cm Object distance for L_2, u_2 = v_1 - d = 15 - 3 = +12 cm Focal length, f_2 = -10 cm Using the lens formu

Question 3

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

Accepted Answer

According to the rules of refraction for spherical lenses, a ray of light parallel to the principal axis of a concave lens diverges after refraction. When this refracted ray is extended backwards, it appears to diverge from the principal focus located on the same side of the lens as the object. By standard convention, the principal focus on the object side (left side) is termed the first principal focus (F_1). Thus, the ray appears to diverge from the first principal focus. Answer: appears to di

Question 4

Consider three media P, Q and R with refractive indices 1, 1.25, and 1.5, respectively. The medium Q having a thickness of 5 cm is placed between extended media P and R as shown in the figure. An obje

Accepted Answer

The object O is placed at the center of medium Q, which has a thickness of 5 cm . Therefore, the actual depth of the object from both the P-Q interface and the Q-R interface is: d = 5 2 = 2.5 cm The formula for apparent depth when viewed from a medium of refractive index n_ observer into a medium of refractive index n_ object is given by: h_ app = d n_ observer n_ object When viewed from medium P (n_P = 1), the apparent depth h_1 of the object in medium Q (n_Q = 1.25) is: h_1 = 2.5 n_P n_Q = 2.5

Question 5

In a certain camera, a combination of four similar thin convex lenses are arranged axially in contact. Then the power of the combination and the total magnification in comparison to the power (p) and

Accepted Answer

When a combination of lens is used then total power aligned P_ net & =P+P+P+P \ & =4 P aligned Total magnification m _ net = m m m m = m ^4

Question 6

A microscope has an objective of focal length 2 cm , eyepiece of focal length 4 cm and the tube length of 40 cm . If the distance of distinct vision of eye is 25 cm , the magnification in the microsco

Accepted Answer

array ll f _0=2 ~cm & f _e=4 ~cm \ ~L =40 ~cm & D =25 ~cm array In the condition of normal adjustment. aligned m & = L f _0 D f _e \ & = 40 2 25 4 \ & =125 aligned

Question 7

A small telescope has an objective of focal length 140 cm and an eye piece of focal length 5.0 cm . The magnifying power of telescope for viewing a distant object is:

Accepted Answer

f_0=140 ~cm and f_e=5 ~cm For distant object, m= f_0 f_e = 140 5 =28

Question 8

A light ray enters through a right angled prism at point P with the angle of incidence 30^ as shown in figure. It travels through the prism parallel to its base B C and emerges along the face A C. The

Accepted Answer

In prism, r_1+c=A gathered r_1=90^ -c (1)\ c= 1 c= ^2-1 gathered Apply Snell's law, on incidence surface aligned 1 30^ = (r_1 ) 1 1 2 & = (90^ -c ) \ 1 2 & = ^2-1 aligned On squaring 1 4 = ^2-1 ^2= 5 4 = 5 2

Question 9

Given below are two statements: Statement I : Image formation needs regular reflection and/or refraction. Statement II : The variety in colour of objects we see around us is due to the constituent col

Accepted Answer

Regular reflection is necessary for image formation, that is why we can see our image in a mirror but not in wall. Different colours in white light as its constituent are responsible for the variety in colour of objects.

Ray Optics — Previous Year Questions & Solutions