1
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
If the half-life of a radioactive nucleus is 3 days, nearly what fraction of the initial number of nuclei will decay on the third day? (Given, $$\root 3 \of {0.25} \approx 0.63$$)
A
0.63
B
0.5
C
0.37
D
0.13
2
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
An electron accelerated through a potential of 10000 V from rest has a de-Broglie wave length $$\lambda$$. What should be the accelerating potential, so that the wavelength is doubled?
A
20000 V
B
40000 V
C
5000 V
D
2500 V
3
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
The de-Broglie wavelength of an electron is $$0.4 \times {10^{ - 10}}$$ m when its kinetic energy is 1.0 keV. Its wavelength will be $$1.0 \times {10^{ - 10}}$$ m, when its kinetic energy is
A
0.2 keV
B
0.8 keV
C
0.63 keV
D
0.16 keV
4
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Radon-222 has a half-life of 3.8 days. If one starts with 0.064 kg of radon-222 left after 19 days will be
A
0.002 kg
B
0.062 kg
C
0.032 kg
D
0.024 kg
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