Quiz 182 – Physics Questions with Explained Answers

The technique used to transmit audio signals in television broadcasts is :

(a) Amplitude Modulation

(b) Frequency Modulation

(c) Pulse Code Modulation

(d) Time Division Multiplexing

Explanation:

Frequency Modulation is used to transmit audio signals in television broadcasts. Frequency modulated signals have larger bandwidth so that FM signals on the adjacent bands do not interfere. Carrier waves of higher frequency have to be used. In FM transmission, the message signal is in the form of frequency variations of carrier waves. Therefore, the noise, which gets amplitude modulated, does not harm the message signal.

Ans- (b)


 

When the same note is played on a sitar a flute, the sound produce can be distinguished from each other because of the difference in:

(a) Pitch, loudness and quality

(b) Pitch and loudness

(c) Quality only

(d) Loudness only

Explanation:

Musical sound can differ from each other with respect to the following three characteristics:

  1. Loudness (intensity)
  2. Pitch (shrillness)
  3. Quality (timber)

But quality (timber) is that characteristics of a musical sound which enables us to distinguish between two sounds even if they have the same pitch and loudness.

Ans- (c)


 

Given below are two statements, one labeled as Assertion (A) and other labeled as Reason (R):

Assertion (A): A diamond sparkles more than a glass imitation cut to the same shape.

Reason (R): The refractive index of diamond is less than that of glass.

In context of the above two statements, which one of the following is correct?

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not the correct explanation of A

(c) A is true but R is false

(d) A is false but A is true

Explanation:

The refractive index of diamond is very high (approximately 2.47) while the refractive index for the glass is 1.57. Therefore, the initial angel for the ray of light traveling form diamond to air is very low about 24 degrees. The initial angel for the ray of light traveling from glass to air is 39 degree. Moreover the diamonds are usually cut with their faces in such a manner that once a ray of light enters into it, it suffers a large number of total internal reflections at various faces till the angel of incidence inside the diamond remains greater than the critical angel. In total internal reflection 100% of the light reflected back into the same medium. Hence, the object shines. That’s why a diamond sparkles more than a glass imitation cut to the same shape.

Ans- (c)


 

Who among the following anticipated Newton by declaring that all things gravitate to the earth?

(a) Aryabhatta

(b) Varahamihira

(c) Buddhagupta

(d) Brahmagupta

Explanation:

Brahmagupta anticipated Newton by declaring that all things gravitate to the earth.

Ans- (d)


 

Optical fibre works on the principle of :

(a) Total internal reflection

(b) Refraction

(c) Scattering

(d) Interference

Explanation:

Optical fibres works on the principle of total internal reflection. When light is incident at a small angle at one end, it gets refracted into the fibres (or strands) and gets incident on the interface of the fibres and the coating. The angle of interface of incidence being greater than the critical angle. So, the light suffers the internal reflections again till the angle of incidence being greater than the critical angle for the fibre material.

Ans- (a)


 

Suppose a rocketship is from the earth at a speed of 2/10th the velocity of light. A light in the rocketship appears blue to the passengers on the ship. What colour would it appear to an observer on the earth?

(a) Blue

(b) Orange

(c) Yellow

(d) Yellow-orange

Explanation:

In the air or vacuum to any observer, the velocity of light is same. Since, on rocketship light appears blue to an observer so on earth the observer will see the same colour.

Ans- (a)


 

Cryogenic engines find applications in:

(a) Sub- marine propulsion

(b) Frost-free refrigerators

(c) Rocket technology

(d) Researches in superconductivity

Explanation:

Cryogenic engines find applications in rocket technology.

Ans- (c)


 

The clouds float in the atmosphere because of their low:

(a) Temperature

(b) Velocity

(c) Pressure

(d) Density

Explanation: when air rises, it is cooled by expansion. After dew point has reached cooling leads to condensation of water vapour in the atmosphere. Tiny droplets of water vapour which are too small to fall as rain or shower will be suspended in the air and float as clouds.

Ans- (a)


 

An air bubble in water will act like a :

(a) Convex mirror

(b) Convex lens

(c) Concave mirror

(d) Concave lens

Explanation:

An air bubble in water will act like concave lens.

Ans- (d)


 

When a mirror is rotated by an angle X, the reflected ray will rotate by:

(a) 0 Degree

(b) X/2 Degree

(c) X

(d) 2X

Explanation:

For given incident ray, if a plane mirror is rotated through a certain angle, then the reflected ray rotates through twice of that angle. So if a mirror is rotated by an angle X, the reflected ray will rotate by 2X.

Ans- (d)

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3 COMMENTS

  1. Clouds float due to low density rather than temperature. Due to temp difference only heat flows. Also terminal velocity is directly proportional to radius of body. That is why heavy rain drops move faster. If temp is the real factor, you know temp at surface of earth is more than upper layer at which clouds float. Then it is not possible for an object to move from lower temp to higher temp by itself without workdone. Also according to Bernoullis theorem smoke goes upward due to pressure difference not temp.

  2. space ship answer is wrong beacause there will be a Doppler shift in the incoming light from space ship to earth

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