The work function of a photoelectric material is 3.3 eV. The threshold frequency will be equal to
|
(a) 8 |
(b) 8 |
(c) 8 |
(d) 8 |
The work function of a photoelectric material is 3.3 eV. The threshold frequency will be equal to
|
(a) 8 |
(b) 8 |
(c) 8 |
(d) 8 |
(d) 8
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Energy of an electron in an excited hydrogen atom is – 3.4 eV. Its angular momentum will be: h = 6.626
|
(a) 1.11 |
(b) 1.51 |
(c) 2.11 |
(d) 3.72 |
The distance of two points on the axis of a magnet from its centre is 10 cm and 20 cm respectively. The ratio of magnetic intensity at these points is 12.5 : 1. The length of the magnet will be
| (a) 5 cm | (b) 25 cm | (c) 10 cm | (d) 20 cm |
The current conduction in a discharged tube is due to
|
(a) Electrons only |
(b) +ve ions and electrons |
|
(c) – ve ions and electrons |
(d) + ve ions, – ve ions and electrons |
An electron moving with the speed 5
per sec is shooted parallel to the electric field of intensity 1
. Field is responsible for the retardation of motion of electron. Now evaluate the distance travelled by the electron before coming to rest for an instant (mass of e = 9
. charge = 1.6
)
|
(a) 7 m |
(b) 0.7 mm |
(c) 7 cm |
(d) 0.7 cm |
A beam with wavelength
falls on a stack of partially reflecting planes with separation d. The angle q that the beam should make with the planes so that the beams reflected from successive planes may interfere constructively is (where n = 1, 2, ……)
|
(a) |
(b) |
(c) |
(d) |
If R is the Rydberg’s constant for hydrogen the wave number of the first line in the Lyman series will be
|
(a) |
(b) |
(c) |
(d) 2R |