NEET Modern Physics MCQs & PYQs

All electron ejected from a surface by incident of wavelength 200 nm can be stopped before
travelling 1 meter in the direction of a uniform electric field of 4 NC–¹ the work function of the
surface is :

The ratio of momenta of an electron and α-particle which are accelerated from rest by a
potential difference of 100 V is :

In the given nuclear reaction A, B, C, D, E represents

In the given reaction \[_{Z}X^{A}\longrightarrow _{Z}Y^{A’}+n\alpha+n’\beta\]. The ratio (Z/A) will be equal to.

Starting with a sample of pure \[Cu^{66}\], (7/8) of it decays into Zn in 15 minutes. The corresponding half-life is

When monochromatic radiation of intensity I falls on a metal surface, the number of photoelectron and their maximum kinetic energy are N and T respectively. If the intensity of radiation is 2I, the number of emitted electrons and their maximum kinetic energy are respectively : (Assume frequency of radiation to be constant)

The threshold frequency for a photosensitive metal is \[3.3\times 10^{14} Hz\]. If light of frequency \[8.2\times 10^{14} Hz\] is incident on this metal, the cut-off voltage for the photoelectric emission is nearly :

Surface area of \[Al^{27}\] is S0, then surface area of \[Zn^{64}\] is :

A star initially has \[10^{40}\] deuterons. It produces energy via the processes ;

If the average power radiated by the star is \[10^{16}\] W, the deuteron supply of the star is
exhausted in a time of the order of :

A 200 W sodium street lamp emits yellow light of wavelength 0.6 μm. Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is :