Explanation:
No, thermionic emissions and photoelectric emissions are not the same. During thermionic emissions, the electrons are emitted from the metal surface by providing heat energy, whereas, during photoelectric emission light energy is emitted when electrons are emitted from the surface of the metal. So, it is the opposite in operation.
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A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 
away, the number of electrons emitted by photo cathode would
|
(a) Decrease by a factor of 2 |
(b) Increase by a factor of 2 |
|
(c) Decrease by a factor of 4 |
(d) Increase by a factor of 4 |
$10\text{cm}$
$10\sqrt{2}\text{cm}$
$\frac{10}{\sqrt{2}}\text{cm}$
A plano-convex lens is made of refractive index of 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is
|
(a) 400 cm |
(b) 200 cm |
(c) 100 cm |
(d) 50 cm |
Magnifying power of a simple microscope is (when final image is formed at D = 25 cm from eye)
|
(a) |
(b) 1 + |
(c) |
(d) |
The charge on a capacitor of capacitance 10 μF connected as shown in the figure is
|
(a) 20 μC |
(b) 15 μC |
(c) 10 μC |
(d) Zero |
