JEE Main 2018 (Online) 15th April Morning Slot | Dual Nature of Radiation Question 144 | Physics

Two electrons are moving with non-relativistic speed perpendicular to each other. If corresponding de Broglie wavelength are $${\lambda _1}$$ and $${\lambda _2},$$ their de Broglie wavelength in the frame of reference attached to their center of masses :

$${\lambda _{CM}} = {\lambda _1} = {\lambda _2}$$

$${\lambda _{CM}} = {{2{\lambda _1}{\lambda _2}} \over {\sqrt {\lambda _1^2 + \lambda _2^2} }}$$

$${1 \over {{\lambda _{CM}}}} = {1 \over {{\lambda _1}}} + {1 \over {{\lambda _2}}}$$

$${\lambda _{CM}} = \left( {{{{\lambda _1} + {\lambda _2}} \over 2}} \right)$$

JEE Main 2017 (Online) 9th April Morning Slot

MCQ (Single Correct Answer)

-1

A Laser light of wavelength 660 nm is used to weld Retina detachment. If a Laser pulse of width 60 ms and power 0.5 kW is used the approximate number of photons in the pulse are :

[Take Planck's constant h $$=$$ 6.62 $$ \times $$ 10^$$-$$34 Js]

10²⁰

10¹⁸

10²²

10¹⁹

JEE Main 2017 (Online) 8th April Morning Slot

MCQ (Single Correct Answer)

-1

The maximum velocity of the photoelectrons emitted from the surface is v when light of frequency n falls on a metal surface. If the incident frequency is increased to 3n, the maximum velocity of the ejected photoelectrons will be :

less than $$\sqrt 3 $$ v

more than $$\sqrt 3 \,v$$

equal to $$\sqrt 3 \,v$$

JEE Main 2017 (Offline)

MCQ (Single Correct Answer)

-1

A particle A of mass m and initial velocity v collides with a particle B of mass m/2 which is at rest. The collision is head on, and elastic. The ratio of the de-Broglie wavelengths $${\lambda _A}$$ to $${\lambda _B}$$ after the collision is:

$${{{\lambda _A}} \over {{\lambda _B}}} = {1 \over 3}$$

$${{{\lambda _A}} \over {{\lambda _B}}} = 2$$

$${{{\lambda _A}} \over {{\lambda _B}}} = {2 \over 3}$$

$${{{\lambda _A}} \over {{\lambda _B}}} = {1 \over 2}$$

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