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

Total Questions: 50

11. The lens which is thin in the middle and thick at its periphery is called a. [RRB NTPC CBT - I (30/01/2021) Morning]

Correct Answer: (a) Concave Lens
Solution:

Concave Lens. Cylindrical lens - A type of lens that has differing radii in the X and Y axes. Convex lens - a lens that converges rays of light that convey parallel to its principal axis.

12. The blue colour of the sky is due to the: [RRB NTPC CBT - I (03/02/2021) Evening]

Correct Answer: (b) Scattering of light
Solution:

Scattering of light. Other Examples of Scattering - Reddish color of the sun during sunrise and sunset, Danger signals in red color. Examples of refraction of light - Twinkling of stars in a clear sky, Camera lenses, Pool of water appears to be less deep than it actually is. Examples of Dispersion of light - Rainbow formation, Petrol poured in water will show different colours. Examples of Diffraction of light - CD reflecting rainbow colours, Holograms, Bending of light at the corners of the door.

13. The phenomenon of ‘dispersion of light’ into its seven constituent colors was discovered by _______ in 1666. [RRB NTPC CBT - I (09/02/2021) Morning]

Correct Answer: (b) Isaac Newton
Solution:

Isaac Newton. The dispersion of light - The phenomenon of splitting a beam of white light into its seven constituent colours when passed through a transparent medium.

14. Shadows are formed when ____ objects come in the path of light. [RRB NTPC CBT - I ( 15/02/2021 ) Evening]

Correct Answer: (d) opaque
Solution:

Opaque: An object which does not allow any light to pass through it. Example - Wood, stone, metal. Translucent: An object which allows only some light to pass through it. Example - Butter paper, sunglasses, various types of plastics. Transparent - An object which allows all light to pass through it. Example - Air, water, clear glass. Luminous - An object which emits light or energy of their own. Example - Sun, stars, candles.

15. What is the full form of LASER? [RRB NTPC CBT - I (22/02/2021) Evening]

Correct Answer: (d) Light Amplification by Stimulated Emission of Radiation
Solution:

Light Amplification by Stimulated Emission of Radiation. It is a device that emits coherent and focused light through a process called stimulated emission. It produces a narrow and intense beam of light that is typically monochromatic (single wavelength) and highly directional. Examples of laser applications - Laser eye surgery, laser printers, barcode scanners, fiber optic communications.

16. Which type of mirrors are commonly used in torches, searchlights and vehicle headlights to get powerful parallel beams of light? [RRB NTPC CBT - I (27/02/2021) Evening]

Correct Answer: (c) Concave
Solution:

Concave mirror (converging mirror). When light rays fall they are reflected inward and converge at a point called the focal point. Concave mirror uses: Shaving mirrors, Astronomical telescopes, Headlights, Solar furnaces.

17. Which kind of mirror is used as rear view wing mirrors in vehicles? [RRB NTPC CBT - I (03/03/2021) Evening]

Correct Answer: (d) Convex
Solution:

Convex. Uses of Convex mirrors - Optical instruments, Calling bell, Magnifying glasses, in Sunglasses. Uses of Plane mirrors - Looking Glasses, Periscopes and kaleidoscopes.

18. What is the time difference between the actual passing of the sun over the horizon and our being able to see the image of it on earth? [RRB NTPC CBT - I (03/03/2021) Evening]

Correct Answer: (d) 2 min
Solution:

2 min. We are able to see the sun 2 minutes before the actual sunrise and 2 minutes after the actual sunset due to Refraction of light by the atmosphere. Time taken by the sunlight to reach the earth’s surface is 8 minutes 20 seconds. Time taken by moonlight to reach the earth’s surface is about 1.3 seconds.

19. Which of the following can produce a virtual image larger than the object? [RRB NTPC CBT - I (08/03/2021) Evening]

Correct Answer: (d) Concave mirror
Solution:

Concave mirror - When the object is placed between the pole and focus of the mirror. Convex mirrors and concave lenses always produce virtual images that are smaller than the object. Plane mirrors produce virtual images that are the same size as the object.

20. Light travels in a : [RRB NTPC CBT - I (12/03/2021) Morning]

Correct Answer: (c) straight line
Solution:

Straight Line. Light is electromagnetic radiation and is both wave-like and particle-like. Properties: It is demonstrated by phenomena such as the photoelectric effect and the double-slit experiment. Light exhibits interference and diffraction phenomena, demonstrating its wave nature. Light can be described as discrete packets of energy called photons. Inventor of the Light bulb - Thomas Edison.