Question Detail

Which law states, "The rate of loss of heat by a body is directly proportional to the difference in temperature between the body and the surroundings."

Doppler's Effect
Newton's law of cooling
Kirchhoff's Law
Stefan's Law

Answer: Option B

Explanation:

Doppler's Effect - The Doppler effect can be described as the effect produced by a moving source of waves in which there is an apparent upward shift in frequency for observers towards whom the source is approaching and an apparent downward shift in frequency for observers from whom the source is receding.

Kirchhoff's Law - Kirchhoff's Law signifies that good absorbers are good emitters.

Stefan's Law - The radiant energy emitted by a black body per unit area per unit time is directly proportional to the fourth power of its absolute temperature.

1. Which law is also called law of inertia ?

Newton first law
Newton second law
Newton third law
All of above

Answer: Option A

2. Force of attraction between the molecules of different substances is called

Surface tension
Cohensive force
Adhesive force
None of above

Answer: Option C

Explanation:

Cohensive force - Force of attraction between the molecules of same substance is called Cohensive force.

3. If lift is going up with acceleration, the apparent weight of a body is

may be more or less than true weight
equal to the true weight
less than the true weight
more than the true weight

Answer: Option D

4. What is the relation between wavelength, frequency and velocity ?

velocity of wave = frequency * wavelength
velocity of wave = frequency/wavelength
velocity of wave = wavelength/frequency
None of above

Answer: Option A

5. Which of following in not a property of cathode ray.

Cathode rays are invisible and travel in a straight line.
These rays can ionise gases.
These rays can penetrate through thin metal foils.
These rays make materials cool on which they fall.

Answer: Option D

Explanation:

These rays heat the materials on which they fall.