1
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
The activity of a radioactive sample falls from 700 s–1 to 500 s–1 in 30 minutes. Its half life is close to:
A
62 min
B
66 min
C
72 min
D
52 min
2
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
An electron (of mass m) and a photon have the same energy E in the range of a few eV. The ratio of the de-Broglie wavelength associated with the electron and the wavelength of the photon is (c = speed of light in vaccuum)
A
$${1 \over c}{\left( {{{2E} \over m}} \right)^{{1 \over 2}}}$$
B
$${1 \over c}{\left( {{E \over {2m}}} \right)^{{1 \over 2}}}$$
C
$${\left( {{E \over {2m}}} \right)^{{1 \over 2}}}$$
D
$$c{\left( {2mE} \right)^{{1 \over 2}}}$$
3
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Mass per unit area of a circular disc of radius $$a$$ depends on the distance r from its centre as $$\sigma \left( r \right)$$ = A + Br . The moment of inertia of the disc about the axis, perpendicular to the plane and assing through its centre is:
A
$$2\pi {a^4}\left( {{A \over 4} + {{aB} \over 5}} \right)$$
B
$$\pi {a^4}\left( {{A \over 4} + {{aB} \over 5}} \right)$$
C
$$2\pi {a^4}\left( {{{aA} \over 4} + {B \over 5}} \right)$$
D
$$2\pi {a^4}\left( {{A \over 4} + {B \over 5}} \right)$$
4
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
In the figure, potential difference between A and B is : JEE Main 2020 (Online) 7th January Evening Slot Physics - Semiconductor Question 125 English
A
10 V
B
5 V
C
zero
D
15 V
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