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AP Polycet (Polytechnic) 2025 Previous Question Paper with Answers And Model Papers With Complete Analysis

71) The image formed by a plane mirror is always:

A) virtual and erect

B) virtual and inverted

C) real and erect

D) real and inverted

View Answer

A) virtual and erect
Explanation:The image formed by a plane mirror is always
→ virtual and erect

72) The distance between the pole and the principal focus of a spherical mirror is called:

A) image distance

B) object distance

C) focal length

D) radius of curvature

View Answer

C) focal length
Explanation:Distance between pole and principal focus
→ focal length

73) A diminished, virtual and erect image is formed by a

A) concave mirror

B) convex mirror

C) plane mirror

D) planoconcave mirror

View Answer

B) convex mirror
Explanation:A diminished, virtual, erect image is formed by
→ convex mirror

74) The mirror used by a dentist to see a large image of the teeth of the patients is

A) concave mirror

B) convex mirror

C) plane mirror

D) plano-convex mirror

View Answer

A) concave mirror
Explanation:Mirror used by dentists
→ concave mirror

75) A ray of light travelling in air enters obliquely into water. This light ray

A) bends away from the normal

B) passes through the normal at the surface of separation

C) bends towards the normal

D) travels straight without bending

View Answer

C) bends towards the normal
Explanation:Light bends towards the normal when entering water from air
→ bends towards the normal

76) The focal length of a spherical mirror is 10cm. Its radius of curvature is:

A) 10cm

B) 5cm

C) 20cm

D) 0.2cm

View Answer

C) 20cm
Explanation: $f = \frac{R}{2} \Rightarrow R = 2f = 20 \, \text{cm}$
→ 20cm

77) An object placed between the principal focus and center of curvature of a convex lens forms an image:

A) beyond the center of curvature

B) at infinity

C) at the principal focus

D) between principal focus and center of curvature

View Answer

C) at the principal focus
Explanation:Object between F and 2F (focus and center of curvature) in convex lens → image is beyond 2F
→ beyond the center of curvature

78) The power of a lens is 4D.Its focal length is

A) 0.25cm

B) 2.5cm

C) 25cm

D) 0.025cm

View Answer

C) 25cm
Explanation:Power $P = \frac{100}{f(\text{cm})} \Rightarrow f = \frac{100}{4} = 25 \, \text{cm}$
→ 25cm

79) If the height of the image is equal to the height of an object placed near a spherical lens, then the magnification m is

A) less than 1

B) greater than 1

C) equal to 1

D) equal to zero

View Answer

C) equal to 1
Explanation:Image height = object height → magnification = 1
→ equal to 1

80) An object is placed at a distance of 30cm from a concave lens of focal length 20cm.
The image distance is:

A) 75cm

B) 60cm

C) 12cm

D) 50cm

View Answer

C) 12cm
Explanation:Use lens formula:
$\frac{1}{f} = \frac{1}{v} - \frac{1}{u}, \quad f = -20\,\text{cm},\, u = -30\,\text{cm} \Rightarrow \frac{1}{v} = \frac{1}{f} + \frac{1}{u} = -\frac{1}{20} - \frac{1}{30} = -\frac{1}{12} \Rightarrow v = -12\,\text{cm}$
Image distance = 12cm
→ 12cm

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