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TS Polycet (Polytechnic) 2021 Previous Question Paper with Answers And Model Papers With Complete Analysis

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61)To find normal to curved surface at a point, join that point and

A) Focus (F)

B) Pole (P)

C) Centre of curvature C.

D) Any point on principal axis

View Answer

C) Centre of curvature C.
Explanation:Normal to a curved surface at a point is drawn by joining that point to the centre of curvature (C).

62)When a set of parallel rays of light inclined at 15° to the principal axis, are incident on a convex lens, they

A) Converge at focus (F)

B) Diverge from focus (F)

C) Converge to a point on focal plane

D) Diverge from a point on focal plane

View Answer

C) Converge to a point on focal plane
Explanation:Parallel rays inclined at 15° converge to a point on the focal plane, not directly at F.
Answer: Converge to a point on focal plane

63)Focal plane of a spherical mirror is

A) Line joining pole (P) and focus (F) of the mirror

B) Plane perpendicular to the principal axis at focus (F)

C) Plane perpendicular at centre of curvature C.

D) Plane parallel to the principal axis

View Answer

B) Plane perpendicular to the principal axis at focus (F)
Explanation:Focal plane is perpendicular to the principal axis at the focus.
Answer: Plane perpendicular to the principal axis at focus (F)

64)Dentist uses this mirror to examine teeth of patients

A) Concave mirror

B) Convex mirror

C) Plane mirror

D) None of the above

View Answer

A) Concave mirror
Explanation:Dentists use concave mirrorsto get a magnified, erect image.
Answer: Concave mirror

65)If object and image lie on the same side of a mirror, the mirror is

A) Concave

B) Convex

C) Plane

D) None of the above

View Answer

A) Concave
Explanation:If both object and image are on same side, it must be a concave mirrorforming a real or magnified virtual image.
Answer: Concave

66)When distance between object and screen s more than 4 times the focal length, in many positions of the convex lens, images is sharp

A) 1

B) 2

C) 3

D) 4

View Answer

B) 2
Explanation:If the object–screen distance is more than 4f, a convex lens can produce a sharp image in twopositions (lens formula).
Answer: 2

67)If a light ray passing through centre of curvature C. of a mirror is incident on the mirror, the reflected ray's path is [b, c]

A) Through focus (F)

B) Through centre of curvature C.

C) Retraces the path And Through centre of curvature C.

D) Through any point

View Answer

C) Retraces the path And Through centre of curvature C.
Explanation:A ray passing through Cstrikes the mirror perpendicularly and retraces its path.
Answer: Retraces the path And Through centre of curvature C.

68)If magnification is equal to one, it means

A) Image is smaller than object

B) Image is larger than object

C) Image is of the same size as that of object

D) Image is point size

View Answer

C) Image is of the same size as that of object
Explanation:Magnification = 1 ⇒ Image size = Object size
Answer: Image is of the same size as that of object

69)An object is placed at a certain distance on the principal axis of a concave mirror. If the image distance (v) is 30 cm and radius of curvature (R) of the mirror is 20 cm, find the object distance (u)

A) 10 cm

B) 15 cm

C) 30 cm

D) 7.5 cm

View Answer

B) 15 cm
Explanation:Use mirror formula:
$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}, \quad R = 2f ⇒ f = 10\,\text{cm},\ v = +30\,\text{cm}$

$\frac{1}{10} = \frac{1}{30} + \frac{1}{u} ⇒ \frac{1}{u} = \frac{1}{10} - \frac{1}{30} = \frac{2}{30} ⇒ u = 15\,\text{cm}$

Answer: 15 cm

70)Which part of our eye is responsible for image formation

A) Cornea

B) Crystalline lens

C) Aqueous humor

D) Iris

View Answer

B) Crystalline lens
Explanation:Image formation happens on the retina, but among options, the crystalline lensfocuses light on the retina.
Answer: Crystalline lens

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