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Directions: Study the following questions carefully and choose the right answer.
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1
A ray of light is incident on a plane mirror at an angle 300 with the normal at the point of incidence. The ray will be deviated from its incidence direction by what angle?
» Explain it
B
The given situation can be shown as

When a ray of light OA is incident on a plane mirror at an angle of incidence 300, then it gets reflected (OB) with angle of reflection 300, by the laws of reflection.

Hence, the ray will be deviated from its incidence direction by an angle of 600.

Reflection from plane mirror:

2
Who gave the first evidence of the big-bang theory?
» Explain it
A
Edwin Hubble gave the first evidence of the big-bang theory.

3
The density of water varies with temperature which helps the aquatic animals to live in cold water. At what temperature is the density of water maximum?
» Explain it
D
The density of water varies inversely with volume of water, At 40 C, volume of water is minimum and hence density of water is maximum at 40 C.
4
Why is it difficult to see through fog?
» Explain it
B
It is difficult to see through fog, because the rays of light are scattered by the fog droplets.
5
Assertion (A) Steam is more harmful for human body than the boiling water in case of burn.

Reason (R) Boiling water contains more heat than steam.

Codes:
» Explain it
C
When 1 kg of steam condenses to water, it gives up to 22.6 × 105 J of heat, that’s why steam burns are more serious than burns from boiling water even though both are at 1000C.