Metallic solids are always opaque because
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(a) Solids effect the incident light |
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(b) Incident light is readily absorbed by the free electron in a metal |
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(c) Incident light is scattered by solid molecules |
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(d) Energy band traps the incident light |
(b) Incident light is readily absorbed by the free electron in a metal
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The potential gradient at which the dielectric of a condenser just gets punctured is called
|
(a) Dielectric constant |
(b) Dielectric strength |
(c) Dielectric resistance |
(d) Dielectric number |
In the following circuits PN-junction diodes D1, D2 and D3 are ideal for the following potential of A and B, the correct increasing order of resistance between A and B will be
(i) – 10 V, – 5V (ii) – 5V, – 10 V (iii) – 4V, – 12V
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(a) (i) < (ii) < (iii) |
(b) (iii) < (ii) < (i) |
(c) (ii) = (iii) < (i) |
(d) (i) = (iii) < (ii) |
Which of the following rays has the maximum frequency
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(a) Gamma rays |
(b) Blue light |
(c) Infrared rays |
(d) Ultraviolet rays |
An object 1 cm tall is placed 4cm infront of a mirror. In order to produce an upright image of 3cm height one needs a
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(a) Convex mirror of radius of curvature 12 cm |
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(b) Concave mirror of radius of curvature 12 cm |
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(c) Concave mirror of radius of curvature 4 cm |
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(d) Plane mirror of height 12 cm |