The work function for tungsten and sodium are 4.5 eV and 2.3 eV respectively. If the threshold wavelength λ for sodium is 
, the value of λ for tungsten is
|
(a) 5893 Å |
(b) 10683 Å |
(c) 2791 Å |
(d) 528 Å |
(c) 2791 Å
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Hydrogen atom emits blue light when it changes from n = 4 energy level to the n = 2 level. Which colour of light would the atom emit when it changes from the n = 5 level to the n = 2 level
|
(a) Red |
(b) Yellow |
(c) Green |
(d) Violet |
Three charges Q, +q and +q are placed at the vertices of a right-angled isosceles triangle as shown. The net electrostatic energy of the configuration is zero if Q is equal to
|
(a) |
(b) |
(c) -2q |
(d) +q |
The wavelength of light emitted from second orbit to first orbits in a hydrogen atom is
|
(a) 1.215 |
(b) 1.215 |
(c) 1.215 |
(d) 1.215 |
A charge q is located at the centre of a cube. The electric flux through any face is
|
(a) |
(b) |
(c) |
(d) |
Consider telecommunication through optical fibres. Which of the following statements is not true
|
(a) Optical fibres may have homogeneous core with a suitable cladding |
|
(b) Optical fibres can be of graded refractive index |
|
(c) Optical fibres are subject to electromagnetic interference from outside |
|
(d) Optical fibres have extremely low transmission loss |
