Assertion:   When hot  water  is  poured  in  a  beaker of  thick  glass,  the  beaker cracks. 

Reason:  Outer surface of the beaker expands suddenly.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

If the temperature of a black body increases from 7°C to 287°C then the rate of energy radiation increases by

• ${\left(\frac{287}{7}\right)}^4$

• 16

• 4

• 2

Faraday law of electrolysis indirectly shows

• quantisation of charge

• quantisation of angular momentum

• quantisation of current

• quantisation of viscosity

Assertion:  A hollow metallic closed container maintained at a uniform temperature can act as a source of black body radiation. 

Reason:  All metals act as black bodies.

• If both assertion and reason are true and reason is the correct explanation of assertion 

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion:  A brass tumbler feels much colder than a wooden tray on a chilly day. 

Reason: The thermal conductivity of brass is more than the thermal conductivity of wood.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Three objects coloured black, gray and white can withstand hostile conditions upto 2800^°C. These objects are thrown into a furnace where each of them attains a temperature of 2000^°C. Which object will glow brightest?

• The white object

• The black object

• All glow with equal brightness

• Gray object

Assertion: Perspiration from human body helps in cooling the body.

Reason: A thin layer of water on the skin enhances its emissivity.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation of the assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statements

158.

Which of the following is an amorphous solid?

• glass

• diamond

• salt

• sugar

Assertion: For higher temperatures the peak emission wavelength of a black body shifts to lower wavelengths. 

Reason:  Peak emission wavelengths of a blackbody is proportional to the fourth power of temperature.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Suppose the sun expands so that its radius becomes 100 times its present radius and its surface temperature becomes half of its present value. The total energy emitted by it then will increase by a factor of

• 10⁴

• 625

• 256

• 16