Railway Science (Physics-Light and Optics) (Part-IV)

Total Questions: 50

1. Ratio of Sin i and Sin r is known as: [RRC Group D 11/10/2022 (Morning)]

Correct Answer: (c) refractive index
Solution:

Refractive index. It can be equated to the ratio of speed of light in the two mediums.

2. Excessive curvature of eye lens leads to _______ [RRB NTPC CBT - I (29/12/2020) Morning]

Correct Answer: (d) myopia
Solution:

Myopia (Nearsightedness) - Image forms right in front of the retina rather than on its surface. It can be corrected by using a concave lens (Diverging lens). Hypermetropia (Farsightedness) - Nearby objects appear blurred, It can be corrected using a convex lens (Converging lens ). Cataract - Cloudy area in the lens of our eye. Color blindness - The condition is often inherited (trouble in identifying colors like blue, green and red).

3. Which of the two colours of spectrum forms the extremes? [RRB NTPC CBT - I (07/01/2021) Evening]

Correct Answer: (a) Violet and Red
Solution:Violet and Red. The spectrum of colours (VIBGYOR) Violet, Indigo, Blue, Green, Yellow, Orange, Red. The wavelength of light defines the colour of the light and in VIBGYOR, wavelength increases from left to right. Violet colour has minimum wavelength while Red colour has a maximum wavelength.

4. Which type of mirror is used by dentists to see large images of patients' teeth? [RRB NTPC CBT - I (09/01/2021) Morning]

Correct Answer: (a) Concave mirror
Solution:

Concave mirror: Used as Vehicle headlights, Shaving mirrors, Solar furnaces, Searchlights, Microscopes, flashlights, torches, etc. Uses of Convex Mirror - In the rear-view mirrors of all the vehicles, Inside buildings, Magnifying glass, Security purposes etc.

5. The ability of the eyes to focus on both, near and distant objects, by adjusting its focal length, is called the _____ of the eye. [RRB NTPC CBT - I (11/01/2021) Morning]

Correct Answer: (a) accommodation
Solution:

Accommodation - This process is achieved by the ciliary muscles in the eye, which change the shape of the lens to alter its focal length. The least distinct vision is 25 cm for normal healthy eyes. Focal length - The distance between the pole and the principal focus of a spherical mirror.

6. Travellers in deserts often tend to have an optical illusion of a sheet of water where none actually exists. What is this called? [RRB NTPC CBT - I (11/01/2021) Evening]

Correct Answer: (c) Mirage
Solution:

Mirage - An optical phenomenon caused by the total internal reflection of light from distant objects. When light passes from cold air (denser) to hot air (rarer), it bends away from the normal and undergoes total internal reflection, thus causing an illusion to the observer that light is coming from the ground.

7. The ability of a medium to refract light is also expressed in terms of its: [RRB NTPC CBT - I (12/01/2021) Evening]

Correct Answer: (b) optical density
Solution:

Optical density. Optical illusion is basically a difference between reality and what our brain thinks it's observing. Mass density is the mass per unit volume of a substance. Refraction is the change in the direction of a wave passing from one medium to another.

8. The center of the reflecting surface of a spherical mirror is a point called: [RRB NTPC CBT - I (12/01/2021) Evening]

Correct Answer: (b) pole
Solution:

Pole. It is the midpoint of the aperture of the spherical mirror and usually represented by the letter P. Principal axis is the line passing through the optical center and centers of curvature of the faces of a lens or a curved mirror. The centre of curvature is the centre of the sphere of which the spherical mirror is a part. It is denoted by 'C'. When rays from infinity come in parallel to the optical axis of a spherical mirror, they are bent so that they either converge and intersect at a point, or they seem to diverge from a point. The point of convergence or divergence is called the focus.

9. Which of the following principles is related to solar power systems? [RRB NTPC CBT - I (13/01/2021) Morning]

Correct Answer: (a) Photovoltaic effect
Solution:

Photovoltaic effect. The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. The theory of photokinetic effects expresses the forces and torques exerted by a beam of light.

10. Which of the following is NOT an example of refraction of light? [RRB NTPC CBT - I (19/01/2021) Morning]

Correct Answer: (c) Red colour of setting sun
Solution:

The red color of the setting sun is an example of the scattering of light. Other Examples of scattering of light - The blue color of the sky, The twinkling of stars, The appearance of a diamond as sparkling, The use of lasers in surgery. Examples of refraction - Pool of water appears to be less deep than it actually is, Camera lenses, Glasses.