1
JEE Main 2021 (Online) 26th February Morning Shift
+4
-1
Given below are two statements : one is labeled as Assertion A and the other is labelled as Reason R.

Assertion A : An electron microscope can achieve better resolving power than an optical microscope.

Reason R : The de Broglie's wavelength of the electrons emitted from an electron gun is much less than wavelength of visible light.

In the light of the above statements, choose the correct answer from the options given below :
A
A is false but R is true.
B
Both A and R are true but R is NOT the correct explanation of A.
C
Both A and R are true and R is the correct explanation of A.
D
A is true but R is false.
2
JEE Main 2021 (Online) 25th February Evening Shift
+4
-1
The wavelength of the photon emitted by a hydrogen atom when an electron makes a transition from n = 2 to n = 1 state is :
A
194.8 nm
B
490.7 nm
C
913.3 nm
D
121.8 nm
3
JEE Main 2021 (Online) 25th February Evening Shift
+4
-1
The stopping potential for electrons emitted from a photosensitive surface illuminated by light of wavelength 491 nm is 0.710 V. When the incident wavelength is changed to a new value, the stopping potential is 1.43 V. The new wavelength is :
A
400 nm
B
329 nm
C
309 nm
D
382 nm
4
JEE Main 2021 (Online) 25th February Morning Shift
+4
-1
An $$\alpha$$ particle and a proton are accelerated from rest by a potential difference of 200V. After this, their de Broglie wavelengths are $$\lambda$$$$\alpha$$ and $$\lambda$$p respectively. The ratio $${{{{\lambda _p}} \over {{\lambda _\alpha }}}}$$ is :
A
8
B
2.8
C
7.8
D
3.8
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