1
NEET 2018
MCQ (Single Correct Answer)
+4
-1
An electron of mass m with an initial velocity $$\overrightarrow v = {v_0}\widehat i$$ (v0 > 0) enters an electric field $$\overrightarrow E = - {\overrightarrow E _0}\widehat i$$ (E0 = constant > 0) at t = 0. If $$\lambda $$0 is its de-Broglie wavelength initially, then its de- Broglie wavelength at time t is
A
$${{{\lambda _0}} \over {\left( {1 + {{e{E_0}} \over {m{v_0}}}t} \right)}}$$
B
$${{\lambda _0}\left( {1 + {{e{E_0}} \over {m{v_0}}}t} \right)}$$
C
$$\lambda $$0t
D
$$\lambda $$0
2
NEET 2018
MCQ (Single Correct Answer)
+4
-1
When the light of frequency 2$${\upsilon _0}$$ (where $${\upsilon _0}$$ is threshold frequency), is incident on a metal plate, the maximum velocity of electrons emitted is v1 . When the frequency of the incident radiation is increased to 5$${\upsilon _0}$$ , the maximum velocity of electrons emitted from the same plate is v2 . The ratio of v1 to v2 is
A
1 : 2
B
1 : 4
C
4 : 1
D
2 : 1
3
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
$${h \over {\sqrt {mkT} }}$$
4
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
$${\lambda _0} = \lambda $$
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