Recently Active Modern Physics Questions

multi correct A neutron collides head on with a stationary hydrogen atom in ground state.Which of the following are correct( take mass of neutron ≈ hydrogen) A) if kinetic energy of neutron is less than 13.6 eV , collision ...

1) A spectroscopic instrument can differntiate 2 close wavelengths λ and λ+Δλ if λ/Δλ = 8000. The instrument is used to study spectral lines of balmer series of hydrogen. find approx how many lines are distinguished by ...

Q) A neutron moving with speed v strikes a hydrogen atom in ground state moving towards it with same speed. Find the minimum kinetic energy of the neutron for which inelastic(complete or partial) collision may occur . (Take m ...

the photoelectrons ejected from the photocathode of a PMT, are said to be of a random count. i.e. for a single given photon hitting the photocathode, the ejection of photoelectrons are sometimes 10 photoelectrons, sometimes 7 ...

1) A radioactive nuclide can decay simultaneously by two different processes which have deacy constants λ1 and λ2 . The effective decay constant of the nuclide is λ. a) λ=λ1 + λ2 b)λ= 1/2 (λ1 + λ2) c) 1/λ = 1/λ1 + ...

1. A small 10W source of ultraviolet light of wavelength 99nm is held at a distance 0.1m from a metal surface. The radius of an atom of the metal is approximately 0.05nm. Find a) the average number of photons striking an atom ...

The electron in a hydraogen atom makes transition n1 to n2 ;n1&n2 principal quantum numbers of two states . assume the bohr model to be valid . the time period of the electron in initial state is 8 times that in the final sta ...

a particle of mass M at rest decays into two particles of masses m1 &m ,having nonzero velocities . the ratio of the de- Broglie wavelengths oof the particles ,λ1/λ2 = ...

Q. An electron in the ground state of the He atom joins the Helium nucleus to form He+ ion. Assuming that electron had zero kinetic energy after the transition, find the wavelength of the photon emitted. ...

Consider the two problems. 1)A perfectly reflecting solid sphere of radius r is kept in the path of a parallel beam of light of large aperture. If the beam carries an intensity I,find the force exerted by the beam on the sphe ...

(1) The work function of a certain metal is 3.31×10–19 J. Then the maximum kinetic energy of photo electrons emitted by incident photons of wave length 5000 Ǻ is (given h = 6.62×10–34 Js, c = 3×108 ms–1, e = 1.6×10 ...

Ques. A motor car is going due north at the speed of 50 km\hr. It makes a 90° left turn without changing its speed. The change in velocity is about A. 50km\hr towards west B.70 km\hr towards south west C.70km\hr towards nort ...

On full moon day, moon rises exactly when sun sets, say 6 p.m. in the month of June. At what time the moon will rise on very next day? a) 12/14 hours after 6 p.m. b) 14/12 hours after 6 p.m. c) 14/12 hours before 6 p.m. d) at ...

27. Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate ? (a) The number of free electrons for conduction is significant only in Si and ...

Why does the characteristic spectrum(they occupy the peaks) have more relative intensity than Continous spectrum?Secondly why does Kalpha occupy a higher peak than Kbeta whereas the energy gap in the latter case is more? ...

Ionisation energy of He+ is 19.6 × 10–18 J/atom. The energy of the first stationary state (n = 1) of Li2+ is? Using E = -2.18 x 10^-18 * Z2/n2 gives a wrong answer. What is the problem? ...

The electron in a hyrogen atom makes a transition from n1 -> n2=2. frequency of motion of electron in initial state is 1/27 of that the final state.Then find total no. of transition from n1 to ground state for the gas. ...

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find the correct statements. If Frequency and Intensity of a light source are doubled.Then a)SAtURATioN photocurrent remains almost the same. b)Maximum Kinetic Energy of photoelectrons are doubled. ...

10 gms of 57Co kept in an open container beta-decays with a half life of 270 days. The wt. of the material inside the container after 540 days will be very nearly (A) 10 g (B) 5 g (C) 2.5 g (D) 1.25 g ...

today my sir took a lecture on quantum mechanics , and he told us an amazing thing , which i would like to share with the young enthusiastic brains here The particle theory of light failed to explain the phenomenon like diffr ...

We know that we have to assume light as a collection of particles in some cases.Ok.You know that wind is made of particles.When it passes by you,you feel some jerk.So,if light is made of particles,when it will strike you,you ...

In an experiment on photoelectric effect, light of wavelength 800 nm (less than threshold wavelength) is incident on a cesium plate at the rate of 5.0 W .The potential of the collector plate is made sufficiently positive with ...

Consider a point source emitting a-particles and receptor of area 1 cm2 placed 1 m away from source. Receptor records any α-particle falling on it. If the source contains N0 = 3.0 × 1016 active nuclei and the receptor recor ...

in the production of x-rays,what happens if the electron that is sent hits the nucleus of the heavy metal atom. ...

1)Two photons having a) equal wavelength have equal linear momenta b)equal energies have equal linear momenta c)equal frequencies have equal linear momenta d)equal linear momenta have equal wavelength. ans (d) now here if (d) ...

In a uranium ore sample, the ratio of U238 to Pb206 nuclei is 1/3 Assuming that all the lead present in the ore is final stable product of U238 , find the age of the ore (in 109 year) if half life of U238 is 4.5 × 109 year. ...

Q.It is given in theory books that the magnitude of photoelectric current is independent of the frequency of incident radiation . My doubt : If frequency is increased , each electron's energy increases which means some of the ...

1) A point source of light is placed at the centre of curvature of a hemispherical surface.the radius if curvature is r and the inner surface is completely reflecting.Find the force on the hemisphere due to the light falling ...

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