Assertion: In a pressure cooker the water  is brought to boil. The cooker is then removed from the stove. Now on removing the lid of the pressure cooker, the water starts boiling again. 

Reason: The impurities in water bring down its boiling point.

• 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: The melting point of ice decreases with increase of pressure. 

Reason: Ice contracts on melting

• 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

A black body, at a temperature of  227^°C, radiates heat at  a rate of  20 cal m^-2 s^-1. When its temperature is raised to 727^°C, the heat radiated by it in cal m^-2 s^-1 will be closest to

• 40

• 160

• 320

• 640

Shown below are the black body radiation curves at temperatures  T₁  and  T₂ ( T₂ >  T₁ ). Which of the following plots is correct?

Assertion: Temperatures near the sea coast me moderate.

Reason:  Water has a high thermal conductivity.

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

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

• If assertion is true but reason is false

• If both assertion and reason are false statements

166.

Assertion: It is hotter over the top of a fire than at the same distance on the sides

Reason: Air surrounding the fire conducts more heat upwards.

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

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

• if assertion is true but reason is false

• if both assertion and reason are false statements

According to Wein's displacement law

• λT = constant

• λ/T  = constant

• λ ∝  ( 1/ T² )

• both (b) and (c)

A black body is at a temperature 300 K. It emits energy at a rate, which is proportional to

• 300

• (300)³

• (300)²

• (300)⁴

Assertion: Blue star is at high temperature than red star.

Reason: Wein's displacement law states that T  ∝  ( 1/λ_m ).

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

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

• If the assertion is true but the reason is false.

• If both assertion and reason are false.

Assertion:  The earth without its atmosphere would be inhospitably cold.

Reason: All heat would escape in the absence of atmosphere.

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

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

• If the assertion is true but the reason is false.

• If both assertion and reason are false.