TS Polycet (Polytechnic) 2022 Previous Question Paper with Answers And Model Papers With Complete Analysis

71) For a convex lens magnification of virtual image is possible only when the object distance is

A) equal to F
B) greater than F
C) less than F
D) none of the above

View Answer

C) less than F

Explanation:For convex lens to form virtual image, object must be closer than F
less than F

72) What is the focal length of a plano-convex lens if ‘R’ is the radius of curvature and ‘n’ is the refractive index?

A) f=R
B) $f=\frac R2$
C) $f=\frac R{n-1}$
D) $f=\frac{n-1}R$

View Answer

C) $f=\frac R{n-1}$

Explanation:Plano-convex lens focal length:
$f = \frac{R}{n - 1}$

73) What is lens maker’s formula?

A) $\frac1f=\left(n-1\right)\left(\frac1{R_1}+\frac1{R_2}\right)$
B) $\frac1f=\left(n-1\right)\left(\frac1{R_1}-\frac1{R_2}\right)$
C) $\frac1f=\left(n+1\right)\left(\frac1{R_1}+\frac1{R_2}\right)$
D) $\frac1f=\left(n-1\right)\left(\frac1{R_1}-\frac1{R_2}\right)$

View Answer

D) $\frac1f=\left(n-1\right)\left(\frac1{R_1}-\frac1{R_2}\right)$

Explanation:Lens maker’s formula is:
$\frac{1}{f} = (n - 1)\left( \frac{1}{R_1} - \frac{1}{R_2} \right)$

74) The focal length of a lens depends on

A) (1) Radius of curvature
B) (2) Refractive index of the lens
C) (1) and (2)
D) None of the above

View Answer

C) (1) and (2)

Explanation:Focal length depends on both radius of curvature and refractive index

75) The size of the image formed by a convex mirror is always

A) Enlarged
B) Diminished
C) Double size of the object
D) None

View Answer

B) Diminished

Explanation:Convex mirror always gives diminished image
Diminished

Spread the love

Leave a Reply Cancel reply