Ray Optics and Optical Instruments

Ray Optics and Optical Instruments

Easy Questions
Moderate Questions
Difficult Questions

Optics

Ray Optics and Optical Instruments
Wave Optics
  1. A thin prism having refracting angle 10° is made of glass of refractive index 1.42. This prism is combined with another thin prism of glass of refractive index 1.7. This combination produces dispersion without deviation. The refracting angle of second prism should be








  1. View Hint View Answer Discuss in Forum

    For dispersion without deviation (μ - 1)A1 + (μ' - 1)A2 = 0
    | (μ - 1)A1 | = | (μ' - 1)A2 |
    (1.42 – 1) × 10° = (1.7 – 1)A2 ​
    4.2 = 0.7A2
    ​A2 = 6°

    Correct Option: A

    For dispersion without deviation (μ - 1)A1 + (μ' - 1)A2 = 0
    | (μ - 1)A1 | = | (μ' - 1)A2 |
    (1.42 – 1) × 10° = (1.7 – 1)A2 ​
    4.2 = 0.7A2
    ​A2 = 6°

  1. Focal length of a convex lens of refractive index 1.5 is 2 cm. Focal length of the lens when immersed in a liquid of refractive index of 1.25 will be








  1. View Hint View Answer Discuss in Forum

    fa
    		 =
    μg
    		 - 1 =
    1.5
    		 - 1
    μl1.25
    fl(μg - 1)(1.5 - 1)

    =
    1
    5 =
    2
    1
    		5
    2

    fl =
    5
    		fa =
    5
    		 × 2 = 5 cm
    22

    Correct Option: C

    fa
    		 =
    μg
    		 - 1 =
    1.5
    		 - 1
    μl1.25
    fl(μg - 1)(1.5 - 1)

    =
    1
    5 =
    2
    1
    		5
    2

    fl =
    5
    		fa =
    5
    		 × 2 = 5 cm
    22

  1. Focal length  of a convex lens will be maximum for








  1. View Hint View Answer Discuss in Forum

    For red light, focal length of lens is maximum ​because f ∝ λ and λ is maximum for red light.

    Correct Option: D

    For red light, focal length of lens is maximum ​because f ∝ λ and λ is maximum for red light.

  1. A lens is placed between a source of light and a wall. It forms images of area A1 and A2 on the wall for its two different positions. The area of the source of light is​​​








  1. View Hint View Answer Discuss in Forum

    ​Size of images = A1 and A2. From the displacement method, the area of the source of light = √A1 A2 .

    Correct Option: A

    ​Size of images = A1 and A2. From the displacement method, the area of the source of light = √A1 A2 .

  1. An achromatic combination of lenses is formed by joining​








  1. View Hint View Answer Discuss in Forum

    If two or more lenses are combined together in such a way that this combination produces images of different colours at the same point and of the same size, then this property is called ‘achromatism’. Concave and convex type of lenses are used for this combination.

    Correct Option: C

    If two or more lenses are combined together in such a way that this combination produces images of different colours at the same point and of the same size, then this property is called ‘achromatism’. Concave and convex type of lenses are used for this combination.