- AThe strips of foils opens up.
- BThe strips of foils close.
- CThe strips open and close simultaneously.
- DThe strips neither open nor close.
Explanation:
When a charged body is brought near the top conducting disc of an electroscope, the disc gets induced with charges. These charges run down to the metal strips hanging from the paper clip. Now as both the strips get similar charge, those repel each other and thus open up.
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In vacuum an electron of energy 10 keV hits tungsten target, then emitted radiation will be
|
(a) Cathode rays |
(b) X-rays |
(c) Infrared rays |
(d) Visible spectrum |
A parallel plate air capacitor has a capacitance of 100 μμF. The plates are at a distance d apart. If a slab of thickness t( t ≤ d) and dielectric constant 5 is introduced between the parallel plates, then the capacitance will be
|
(a) 50 μμF |
(b) 100 μμF |
(c) 200 μμF |
(d) 500 μμF |
The colour sequence in a carbon resistor is red, brown, orange and silver. The resistance of the resistor is
|
(a) 21 × 103 ± 10% |
(b) 23 × 101 ± 10 % |
(c) 21 × 103 ± 5% |
(d) 12 × 103 ± 5% |
In Young’s double slit experiment the wavelength of light was changed from 7000 Å to 3500 Å. While doubling the separation between the slits which of the following is not true for this experiment
|
(a) The width of the fringes changes |
|
(b) The colour of bright fringes changes |
|
(c) The separation between successive bright fringes changes |
|
(d) The separation between successive dark fringes remains unchanged |
Hydrogen (H), deuterium (D), singly ionized helium (
and doubly ionized lithium (Li) all have one electron around the nucleus. Consider n =2 to n = 1 transition. The wavelengths of emitted radiations are
and
respectively. Then approximately
|
(a) |
(b) 4 |
|
(c) |
(d) |