- ADiscontinuity.
- BPoor conductivity.
- CNeedle end.
- DLow melting point.
Explanation:
Needle end can arrest the lightning easily. Besides, the device must provide a continuous path to electricity so that current passes to ground. It must have a high melting point else it will meltdown due to the heat generated during carrying lightning current.
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Dark lines on solar spectrum are due to
|
(a) Lack of certain elements |
|
(b) Black body radiation |
|
(c) Absorption of certain wavelengths by outer layers |
|
(d) Scattering |
A slit of width a is illuminated by white light. For red light (λ = 6500 Å), the first minima is obtained at θ = 30°. Then the value of a will be
|
(a) 3250 Å |
(b) 6.5 |
(c) 1.24 microns |
(d) 2.6 |
The variation of the intensity of magnetisation (I) with respect to the magnetising field (H) in a diamagnetic substance is described by the graph

|
(a) OD |
(b) OC |
(c) OB |
(d) OA |
Which of the following statement is wrong
|
(a) Infrared photon has more energy than the photon of visible light |
|
(b) Photographic plates are sensitive to ultraviolet rays |
|
(c) Photographic plates can be made sensitive to infrared rays |
|
(d) Infrared rays are invisible but can cast shadows like visible light rays |
The unit of magnetic flux is
|
(a) |
(b) Weber |
(c) Henry |
(d) Ampere/m |