51.

Mass of the proton is 1840 times that of electron. It is accelerated through a potential difference of 1V. Find its kinetic energy.

• 6 eV

• 2 eV

• 10 eV

• 1 eV

The work function of a metal is 3.4 eV. If the frequency of incident radiation is increased to twice, then the work function of the metal becomes

• 3.4 eV

• 7.2 eV

• 6.8 eV

• 1.7 eV

If red light is replaced by white light then width of diffraction pattern will

• increases

• decreases

• a central white band is obtained

• no effect

In Planck's oscillator energy is given as

     E = $\frac{\mathrm{h\nu }}{\exp \left({\displaystyle \frac{\mathrm{h\nu }}{\mathrm{Kt}}} - 1 \right)}$  If K = 0, then energy would be

• hν

• 0

• Kt

• ∞

A certain radioactive element has a half-life of 20 years. If we have a block with 10 g of the element in it, after how many years will there be just 2.5 g of the element in the block?

• 80 years

• 40 years

• 100 years

• 60 years

Assertion:  Skiers uses air glasses. 

Reason:  Light reflected by snow is partially polarised.

• 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 assertion is false but reason is true.

Assertion:  LASER is used to measure distant object as moon. 

Reason: They are highly coherent source of light.

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

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

• If assertion is true but reason is false.

• If assertion is false but reason is true.

Assertion: During reverse biasing a diode doesn't conduct current. 

Reason: It narrows the depletion layer.

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

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

• If assertion is true but reason is false.

• If assertion is false but reason is true.

Assertion: On increasing the frequency of light larger number of photoelectrons are emitted. 

Reason:  The number of electrons emitted depends on the intensity of incident light.

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

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

• If assertion is true but reason is false.

• If assertion is false but reason is true.

Assertion:  Electric appliances with metallic body e.g., heaters, presses etc., have three pin connections, whereas an electric bulb has a two pin connection. 

Reason:  Three pin connections reduce heating of connecting cables.

• 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 assertion is false but reason is true.