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Q:

# When one enters a dark room after being in bright light one is not able to see anything clearly for a while because

 A) the retina of the eye moves forward B) the retina of the eye moves backward C) the iris is unable to dilate the pupil immediately to be able to see things D) the eye has no power of accommodation

Answer:   C) the iris is unable to dilate the pupil immediately to be able to see things

Explanation:

The size of the pupil of the automatically adjusts itself according to the intensity of light passing through it; if the intensity is more, the size is less, if less, it is more. So in our case the pupil should dilate i.e , increase in size to be able to see in the dark. This switchover takes some time. But here the entry into the dark room is immediate. So the eye has no time to adjust itself and hence is not able to see at all for a while.

Subject: Physics
Q:

What is the full form of "RADAR" ?

 A) Radio Detecting and Ranging B) Region Device and Ranging C) Radio Detect and Rangs D) Radio Device and Ranging

Explanation:

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7 433
Q:

If a carrier wave of 1000 kHz is used to carry the signal, the length of transmitting antenna will be equal to _____ ?

 A) 300 m B) 30 m C) 3 m D) 0.3 m

Explanation:

h =   = 3 × 108/106 = 300 m

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7 423
Q:

Quality of transmission depends upon

 A) Nature of signal only B) Nature of medium only C) Both (A) and (B) D) Neither A nor B

Explanation:

Quality of transmission is governed both by nature of signal and nature of communication channel/medium.

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5 395
Q:

The rate of change of linear momentum of a body falling freely under gravity is equal to it's ____ ?

 A) Kinetic Energy B) Weight C) Potential Energy D) Impulse

Explanation:

Rate of change of impulse equals the force . In case of freely falling body the only force is the weight.

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7 522
Q:

A disk and a sphere of same radius but different masses roll on two inclined planes of the same altitude and length. Which one of the two objects gets to the bottom of the plane first ?

 A) Depends on their masses B) Sphere C) Disk D) Both reach at the same time

Explanation:

Time does not depend on mass, else

$\inline \fn_jvn T \prec \sqrt{\left ( 1 +\frac{k^{2}}{R^{2}} \right )}$

$\inline \fn_jvn \frac{k^{2}}{R^{2}}$  => is least for 'sphere' and

hence least time is taken by sphere.