1
NEET 2017
MCQ (Single Correct Answer)
+4
-1
The de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T (kelvin) and mass m, is
A
$${h \over {\sqrt {3mkT} }}$$
B
$${{2h} \over {\sqrt 3 mkT}}$$
C
$${{2h} \over {\sqrt {mkT} }}$$
D
$${h \over {\sqrt {mkT} }}$$
2
NEET 2016 Phase 2
MCQ (Single Correct Answer)
+4
-1
Electrons of mass m with de-Broglie wavelength $$\lambda $$ fall on the target in an X-ray tube. The cutoff wavelength ($$\lambda $$0) of the emitted X-ray is
A
$$\lambda $$0 = $${{2mc{\lambda ^2}} \over h}$$
B
$${\lambda _0} = {{2h} \over {mc}}$$
C
$${\lambda _0} = {{2{m^2}{c^2}{\lambda ^3}} \over {{h^2}}}$$
D
$${\lambda _0} = \lambda $$
3
NEET 2016 Phase 2
MCQ (Single Correct Answer)
+4
-1
Photons with energy 5 eV are incifent on a cathode C in a photoelectric cell. The maximum energy of emitted photoelectrons is 2 eV. When photons of energy 6 eV are incident on C, no photoelectrons will reach the anode A, if the stopping potential of A relative to C is
A
+ 3 V
B
+4 V
C
$$-$$1 V
D
$$-$$3 V
4
NEET 2016 Phase 1
MCQ (Single Correct Answer)
+4
-1
When a metallic surface is illuminated with radiation of wavelength $$\lambda $$, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2 $$\lambda $$, the stopping potential is $${V \over 4}$$. The threshold wavelength for the metallic surface is
A
$${5 \over 2}\lambda $$
B
3$$\lambda $$
C
4$$\lambda $$
D
5$$\lambda $$
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