Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
21. Which of the following is correct about the rate of loss of heat of the body, as per the Newton’s law of cooling?
[A] It is directly proportional to the difference of body’s temperature and the surroundings
[B] It is inversely proportional to the difference of body’s temperature and the surroundings
[C] It is equal to the difference of body’s temperature and the surroundings
[D] None of the above
Show Answer
Correct Answer: A [It is directly proportional to the difference of body’s temperature and the surroundings]
Notes:
According to Newton’s law of cooling, the rate of loss of heat, – dQ/dt of the body is directly proportional to the difference of temperature of the body and the surroundings.
22. What is the refractive index of water?
[A] 1
[B] 1.01
[C] 1.33
[D] 1.78
Show Answer
Correct Answer: C [1.33]
Notes:
The refractive index of water is 1.33. It helps in calculating the angle of incidence and refraction of light while it passes from air to water or vice versa. Refractive index tells us how much the path of light is disrupted when it enters a medium from another.
23. Which of the following is true about a concave lens?
[A] power of a concave lens is positive
[B] power of a concave lens is negative
[C] power of a concave lens is zero
[D] None of the above
Show Answer
Correct Answer: B [power of a concave lens is negative]
Notes:
The power of a convex lens is positive and that of a concave lens is negative.
24. For how long approximately an image persists on the retina before vanishing?
[A] 1/8 seconds
[B] 1/16 seconds
[C] 1/32 seconds
[D] 1 second
Show Answer
Correct Answer: B [1/16 seconds]
Notes:
The impression of an image does not vanish immediately from the retina. It persists there for about 1/16th of a second. So, if still images of a moving object are flashed on the eye at a rate faster than 16 per second, then the eye perceives this object as moving.
25. What number does orange colour represent in the resistance colour code?
[A] 1
[B] 2
[C] 3
[D] 4
Show Answer
Correct Answer: C [3 ]
Notes:
The resistors have a set of co-axial coloured rings on them. The first two bands from the end indicate the first two significant figures of the resistance in ohms. The third band indicates the decimal multiplier. The last band stands for tolerance or possible variation in percentage about the indicated values.
26. Which of the following is a commonly used moderator in a Nuclear reactor?
[A] Heavy water
[B] Graphite
[C] Water
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Commonly used moderators include water, graphite and heavy water.
27. Which of the following metal foils was used in the Rutherford’s alpha particle scattering experiment?
[A] Copper
[B] Silver
[C] Gold
[D] Aluminium
Show Answer
Correct Answer: C [Gold]
Notes:
Rutherford directed beams of alpha particles (which are the nuclei of helium atoms and hence positively charged) at thin gold foil and noted how the alpha particles scattered from the foil.
28. What is the charge of a p-type semiconductor?
[A] Positive
[B] Negative
[C] Neutral
[D] None of the above
Show Answer
Correct Answer: C [Neutral]
Notes:
The number of free electrons is exactly equal to the total number of holes and positively charged ions and a semiconductor, whether intrinsic or doped, is electrically neutral
29. What is the reason for formation of Mirage in desert?
[A] Refraction of light
[B] Reflection of light
[C] Total internal reflection of light
[D] Both Refraction and Total internal reflection of light
Show Answer
Correct Answer: D [Both Refraction and Total internal reflection of light]
Notes:
Mirage is formed due to both Refraction and Total internal reflection of light. A mirage is a naturally occurring optical phenomenon in which light rays bend to produce a displaced image of distant objects or the sky.
30. Which of the following is the distance between the two successive nodes of a standing wave?
[A] 1
[B] 1/2
[C] 3/4
[D] 1/3
Show Answer
Correct Answer: B [1/2]
Notes:
In a stationary wave, the distance between two successive nodes (anti-nodes) is one half wavelengths. Therefore, the distance between a node and the immediate next anti-node is one fourth of a wavelength.
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