Physics Questions and Answers – Part3

21. The impurity atom with which pure silicon should be doped to make a p-type semiconductor are those of
a. Phosphorus
b. boron
c. Antimony
d. Arsenic
Answer
b. boron

22. Which one of the following planets is said to be “twin sister” of the earth?
a. Mercury
b. Venus
c. Mars
d. Jupiter
Answer
b. Venus

23. The spread in colours in a rainbow on sky is primarily due to
a. Disperation of sunlight
b. refraction of sunlight
c. Reflection of sunlight
d. total internal reflection of sunlight
Answer
c. Reflection of sunlight

24. Who among the following gave the first experimental value of G ?
a. Cavendish
b. Copernicus
c. Brook Taylor
d. Albert Einstein
Answer
a. Cavendish

25. Light Emitting Diode (LED) converts
a. Light energy into electrical energy
b. Electrical energy into light energy
c. Thermal energy into light energy
d. Mechanical energy into electrical energy
Answer
b. Electrical energy into light energy

26. Pa(Pascal) is the unit for
A. thrust
B. pressure
C. frequency
D. conductivity
Answer
B. pressure

27. Planets do not twinkle because
A. they emit light of a constant intensity
B. their distance from the earth does not change with time
C. they are very far away from the earth resulting in decrease in intensity of light
D. they are nearer to earth and hence we receive a greater amount of light and, therefore minor variations in the intensity are not noticeable
Answer
D. they are nearer to earth and hence we receive a greater amount of light and, therefore minor variations in the intensity are not noticeable

28. Metals are good conductors of electricity because
A. they contain free electrons
B. the atoms are lightly packed
C. they have high melting point
D. All of the above
Answer
A. they contain free electrons

29. Let a thin capillary tube be replaced with another tube of insufficient length then, we find water
A. will overflow
B. will not rise
C. depressed
D. change its meniscus
Answer
B. will not rise

30. Out of the following pairs, choose the pair in which the physical quantities do not have identical dimension?
A. Pressure and Young’s modules
B. Planck’s constant and Angular momentum
C. Impulse and moment of force
D. Force and rate of change of linear momentum
Answer
C. Impulse and moment of force

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