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1
JEE Main 2021 (Online) 17th March Morning Shift
MCQ (Single Correct Answer)
+4
-1
An electron of mass m and a photon have same energy E. The ratio of wavelength of electron to that of photon is : (c being the velocity of light)
A
$${1 \over c}{\left( {{{2m} \over E}} \right)^{1/2}}$$
B
$${1 \over c}{\left( {{E \over {2m}}} \right)^{1/2}}$$
C
$${\left( {{E \over {2m}}} \right)^{1/2}}$$
D
$$c{(2mE)^{1/2}}$$
2
JEE Main 2021 (Online) 16th March Evening Shift
MCQ (Single Correct Answer)
+4
-1
Calculate the time interval between 33% decay and 67% decay if half-life of a substance is 20 minutes.
A
40 minutes
B
60 minutes
C
13 minutes
D
20 minutes
3
JEE Main 2021 (Online) 16th March Evening Shift
MCQ (Single Correct Answer)
+4
-1
The de-Broglie wavelength associated with an electron and a proton were calculated by accelerating them through same potential of 100 V. What should nearly be the ratio of their wavelengths? (mp = 1.00727u me = 0.00055u)
A
41.4 : 1
B
(1860)2 : 1
C
1860 : 1
D
43 : 1
4
JEE Main 2021 (Online) 16th March Evening Shift
MCQ (Single Correct Answer)
+4
-1
The half-life of Au198 is 2.7 days. The activity of 1.50 mg of Au198 if its atomic weight is 198 g mol$$-$$1 is, (Na = 6 $$\times$$ 1023/mol).
A
240 Ci
B
357 Ci
C
252 Ci
D
535 Ci
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