Optical Instrument MCQs For NEET

Optical instruments help in the magnification of images. The converging lenses used in optical instruments make things appear larger and diverging lenses make images appear smaller. Instruments like the microscope and telescope use multiple lenses to magnify the images.

Q1: A lens which converges a beam of parallel rays to a point is called

1. Diverging (or concave) lens
2. Converging (or convex) lens
3. Plano concave lens
4. Plano-convex lens

Answer: (b) Converging (or convex) lens

Q2: The diameter of a lens is called

1. Focal length
2. Principle axis
3. Aperture
4. Radius of curvature

Answer: (c) Aperture

Q3: In going from a denser to rarer medium a ray of light is

1. Undeviated
2. Bent away from the normal
3. Bent towards the normal
4. polarised

Answer: (b) Bent away from the normal

Q4: The power of a concave lens is

1. Real
2. Virtual
3. Positive
4. negative

Answer: (d) negative

Q5: Magnifying power of a simple microscope

1. Increases with increase in focal length
2. Increases with the decrease in focal length
3. No effect with decrease or increase with the focal length
4. Least distance of distinct vision

Answer: (b) Increases with the decrease in focal length

Q6: Magnification of astronomical telescope is

1. f₀ + f_e
2. f₀/f_e
3. f_e/f₀
4. (1+f₀/f_e)L/f₀

Answer: (b) f₀/f_e

Q7: The magnifying power of an astronomical telescope is 10 and the focal length of its eye-piece is 20 cm. The focal length of its objective will be

1. 200 cm
2. 2 cm
3. 0.5 cm
4. 0.5 x 10^–2 cm

Answer: (a) 200 cm

Q8: The magnifying power of a telescope is 9. When it is adjusted for parallel rays, the distance between the objective and the eye-piece is found to be 20 cm. The focal lengths of the lenses are

1. 18 cm, 2 cm
2. 11 cm, 9 cm
3. 10 cm, 10 cm
4. 15 cm, 5 cm

Answer: (a) 18 cm, 2 cm

Q9: In a compound microscope, magnifying power is 95 and the distance of the object from the objective lens is 1/38 cm. The focal length of the objective lens ¼ cm. What is the magnification of eyepiece?

1. 5
2. 10
3. 100
4. 200

Answer: (a) 5

Q10: A hypermetropic person having “near point” at a distance of 0.75 m puts on spectacles of power 2.5 D. The “near point” now is at

1. 0.75 m
2. 0.83 m
3. 0.26 cm
4. 0.26 m

Answer: (d) 0.26 m

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