Ultraviolet radiations of 6.2eV falls on an aluminium surface (work function 4.2 eV). The kinetic energy in joules of the fastest electron emitted is approximately
|
(a) 3.2 |
(b) 3.2 |
(c) 3.2 |
(d) 3.2 |
(b) 3.2 
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X-rays are not used for radar purpose because
| (a) They are not reflected by the target |
| (b) They are not electromagnetic waves |
| (c) They are completely absorbed by the air |
| (d) They sometimes damage the target |
Electrons move at right angles to a magnetic field of 1.5 
Tesla with a speed of 6 
. If the specific charge of the electron is 1.7 
C/kg. The radius of the circular path will be
|
(a) 2.9 cm |
(b) 3.9 cm |
(c) 2.35 cm |
(d) 3 cm |
When 
ampere current is passed in a tangent galvanometer, there is a deflection of 30° in it. The deflection obtained when 3 amperes current is passed, is
| (a) 30° | (b) 45° | (c) 60° | (d) 75° |
An infinitely long, straight conductor AB is fixed and a current is passed through it. Another movable straight wire CD of finite length and carrying current is held perpendicular to it and released. Neglect weight of the wire
|
(a) The rod CD will move upwards parallel to itself |
|
(b) The rod CD will move downward parallel to itself |
|
(c) The rod CD will move upward and turn clockwise at the same time |
|
(d) The rod CD will move upward and turn anti –clockwise at the same time |
An electron moving towards the east enters a magnetic field directed towards the north. The force on the electron will be directed
|
(a) Vertically upward |
(b) Vertically downward |
|
(c) Towards the west |
(d) Towards the south |
Image formed on the retina is
|
(a) Real and inverted |
(b) Virtual and erect |
|
(c) Real and erect |
(d) Virtual and inverted |
Assertion : The presence of water molecules makes separation of ions easier in electrolyte.
Reason : The presence of water molecules in electrolyte decreases the resistance of electrolyte.
|
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
|
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
|
(c) If assertion is true but reason is false. |
|
(d) If the assertion and reason both are false. |
