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JEE Main 2021 (Online) 20th July Evening Shift
Numerical
+4
-1
A certain metallic surface is illuminated by monochromatic radiation of wavelength $$\lambda$$. The stopping potential for photoelectric current for this radiation is 3V0. If the same surface is illuminated with a radiation of wavelength 2$$\lambda$$, the stopping potential is V0. The threshold wavelength of this surface for photoelectric effect is ____________ $$\lambda$$.
2
JEE Main 2021 (Online) 17th March Morning Shift
Numerical
+4
-1
If 2.5 $$\times$$ 10$$-$$6 N average force is exerted by a light wave on a non-reflecting surface of 30 cm2 area during 40 minutes of time span, the energy flux of light just before it falls on the surface is ___________ W/cm2. (Round off to the Nearest Integer)

(Assume complete absorption and normal incidence conditions are there)
3
JEE Main 2021 (Online) 26th February Evening Shift
Numerical
+4
-1
Two stream of photons, possessing energies equal to twice and ten times the work function of metal are incident on the metal surface successively. The value of ratio of maximum velocities of the photoelectrons emitted in the two respective cases is x : y. The value of x is ___________.