A proton travels few distance in an electric field, then it enters a crossed magnetic field of 1 T and radius 0.2 m, find the velocity of proton

• 0.2 × 10⁸ m s^-1

• 0.2 ×  10⁷ m s^-1

• 0.2 ×  10⁶ m s^-1

• 2 ×  10⁷ m s^-1

Two lens of focal lengths -20 cm and + 10 cm are put in combination, find the power of the combination

• - 1 D

• - 2 D

• + 5 D

• + 2 D

For a nuclear reactor to run in critical condition the reproduction factor k should be

• = 1

• > 1

• < 1

• >>> 1

A far sighted person has his near point 50 cm, find the power of lens he should use to see at 25 cm, clearly.

• + 1 D

• + 2 D

• - 2 D

• - 1 D

S³² absorbs energy and decays into which element after two $\mathrm{\alpha }$-emissions?

• Carbon

• Aluminium

• Oxygen

• magnesium

46.

Direction of electric field in P-N junction diode is

• from P-side to N-side

• From N-side to P-side

• randomly oriented

• electric field does not exist

Among the following which is used to control the rate of reaction of nuclear fissions reactions?

• Water

• Heavy water

• Cadmium

• Graphite

The series corresponding to minimum wavelength transition in H-atom

• Balmer series

• Lyman series

• Paschen series

• Brackett series

Assertion:  When white light fall on the compact disc, multicolours are seen after reflection. 

Reason: CD disc behaves like a prism.

• 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:  For nuclear reactor, it is desirable to have k = 1.

Reason: Sustained chain reaction occur at this critical condition.

• 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.