1
JEE Main 2021 (Online) 25th February Evening Shift
MCQ (Single Correct Answer)
+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
2
JEE Main 2021 (Online) 25th February Evening Shift
MCQ (Single Correct Answer)
+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
3
JEE Main 2021 (Online) 25th February Morning Shift
MCQ (Single Correct Answer)
+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
4
JEE Main 2021 (Online) 24th February Evening Shift
MCQ (Single Correct Answer)
+4
-1
An X-ray tube is operated at 1.24 million volt. The shortest wavelength of the produced photon will be :
A
10$$-$$2 nm
B
10$$-$$1 nm
C
10$$-$$3 nm
D
10$$-$$4 nm
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