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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Two sources give interference pattern which is observed on a screen, D distance apart from the sources. The fringe width is 2w. If the distance D is now doubled, the fringe width will
|
(a) Become w/2 |
(b) Remain the same |
(c) Become w |
(d) Become 4w |
4 eV is the energy of the incident photon and the work function in 2eV. What is the stopping potential
|
(a) 2V |
(b) 4V |
(c) 6V |
(d) 2 |
A glass rod rubbed with silk is used to charge a gold leaf electroscope and the leaves are observed to diverge. The electroscope thus charged is exposed to X-rays for a short period. Then
|
(a) The divergence of leaves will not be affected |
|
(b) The leaves will diverge further |
|
(c) The leaves will collapse |
|
(d) The leaves will melt |
The half life period of radium is 1600 years. The fraction of a sample of radium that would remain after 6400 years is
|
(a) |
(b) |
(c) |
(d) |
A 10 m long wire of 20W resistance is connected with a battery of 3 volt e.m.f. (negligible internal resistance) and a 10 W resistance is joined to it is series. Potential gradient along wire in volt per meter is
|
(a) 0.02 |
(b) 0.3 |
(c) 0.2 |
(d) 1.3 |
If current flowing through shell of previous objective is equal to i, then energy density at a point distance 2R from axis of the shell varies according to the graph
|
(a)
|
(b)
|
(c)
|
(d)
|
An astronomical refractive telescope has an objective of focal length 20m and an eyepiece of focal length 2cm.
