JEE Main 2020 (Online) 3rd September Evening Slot | Dual Nature of Radiation Question 108 | Physics

Two sources of light emit X-rays of wavelength 1 nm and visible light of wavelength 500 nm, respectively. Both the sources emit light of the same power 200 W. The ratio of the number density of photons of X-rays to the number density of photons of the visible light of the given wavelengths is :

$${1 \over {500}}$$

500

250

$${1 \over {250}}$$

JEE Main 2020 (Online) 3rd September Morning Slot

MCQ (Single Correct Answer)

-1

When the wavelength of radiation falling on a metal is changed from 500 nm to 200 nm, the maximum kinetic energy of the photoelectrons becomes three times larger. The work function of the metal is close to :

1.02 eV

0.81 eV

0.61 eV

0.52 eV

JEE Main 2020 (Online) 2nd September Evening Slot

MCQ (Single Correct Answer)

-1

A particle is moving 5 times as fast as an electron. The ratio of the de-Broglie wavelength of the particle to that of the electron is 1.878 $$ \times $$ 10^–4. The mass of the particle is close to

1.2 $$ \times $$ 10^–28 kg

9.1 $$ \times $$ 10^–31 kg

4.8 $$ \times $$ 10^–27 kg

9.7 $$ \times $$ 10^–28 kg

JEE Main 2020 (Online) 9th January Evening Slot

MCQ (Single Correct Answer)

-1

An electron of mass m and magnitude of charge |e| initially at rest gets accelerated by a constant electric field E. The rate of change of de-Broglie wavelength of this electron at time t ignoring relativistic effects is :

$${{ - h} \over {\left| e \right|Et}}$$

$${{ - h} \over {\left| e \right|E\sqrt t }}$$

$${{ - h} \over {\left| e \right|E{t^2}}}$$

$${{\left| e \right|Et} \over h}$$

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