1
JEE Main 2021 (Online) 26th August Evening Shift
+4
-1
The de-Broglie wavelength of a particle having kinetic energy E is $$\lambda$$. How much extra energy must be given to this particle so that the de-Broglie wavelength reduces to 75% of the initial value?
A
$${1 \over 9}$$E
B
$${7 \over 9}$$E
C
E
D
$${16 \over 9}$$E
2
JEE Main 2021 (Online) 26th August Morning Shift
+4
-1
In a photoelectric experiment ultraviolet light of wavelength 280 nm is used with lithium cathode having work function $$\phi$$ = 2.5 eV. If the wavelength of incident light is switched to 400 nm, find out the change in the stopping potential. (h = 6.63 $$\times$$ 10$$-$$34 Js, c = 3 $$\times$$ 108 ms$$-$$1)
A
1.3 V
B
1.1 V
C
1.9 V
D
0.6 V
3
JEE Main 2021 (Online) 27th July Morning Shift
+4
-1
If 'f' denotes the ratio of the number of nuclei decayed (Nd) to the number of nuclei at t = 0 (N0) then for a collection of radioactive nuclei, the rate of change of 'f' with respect to time is given as :

[$$\lambda$$ is the radioactive decay constant]
A
$$-$$ $$\lambda$$ (1 $$-$$ e$$-$$$$\lambda$$t)
B
$$\lambda$$ (1 $$-$$ e$$-$$$$\lambda$$t)
C
$$\lambda$$e$$-$$$$\lambda$$t
D
$$-$$ $$\lambda$$e$$-$$$$\lambda$$t
4
JEE Main 2021 (Online) 25th July Evening Shift
+4
-1
When radiation of wavelength $$\lambda$$ is incident on a metallic surface, the stopping potential of ejected photoelectrons is 4.8 V. If the same surface is illuminated by radiation of double the previous wavelength, then the stopping potential becomes 1.6 V. The threshold wavelength of the metal is :
A
2$$\lambda$$
B
4$$\lambda$$
C
8$$\lambda$$
D
6$$\lambda$$
JEE Main Subjects
Physics
Mechanics
Electricity
Optics
Modern Physics
Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
Mathematics
Algebra
Trigonometry
Coordinate Geometry
Calculus
EXAM MAP
Joint Entrance Examination