Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main 201910 AprilEvening Shift
Exam
JEE Main
Year
2019
Date
10 April
Shift
Evening Shift
Subject
Physics
Chapter
Dual Nature of Matter

JEE Main 2019 · 10 April · Evening Shift · Physics · Dual Nature of Matter

A 2mW laser operates at a wavelength of 500nm . The number of...

A 2mW2mW laser operates at a wavelength of 500nm500nm . The number of photons that will be emitted per second is:
[Given Planck's constant h=6.6×10−34Js,h = 6.6 \times {10}^{- 34}Js, speed of light c=3.0×108m/sc = 3.0 \times {10}^{8}m / s ]

Options

  1. A1.5×10161.5 \times {10}^{16}
  2. B5×10155 \times {10}^{15}
  3. C2×10162 \times {10}^{16}
  4. D1×10161 \times {10}^{16}

Correct answer

B. 5×10155 \times {10}^{15}

Step-by-step solution

P=2mWP = 2mW
λ=500nm\lambda = 500nm
Number of photons will be emitted per second is,
n=P(hcλ)=2×10−3×500×10−96.6×10−34×3×108n = \dfrac{P}{\left(\dfrac{hc}{\lambda}\right)} = \dfrac{2 \times {10}^{- 3} \times 500 \times {10}^{- 9}}{6.6 \times {10}^{- 34} \times 3 \times {10}^{8}}
=5×1015= 5 \times {10}^{15}
Practice Dual Nature of Matter on Quantrex Academy →

More from Dual Nature of Matter

K_1 and K_2 be the maximum kinetic energies of photoelectrons emitted from a surface of a… JEE Main 2026The de Broglie wavelength for an electron accelerated through the potential difference of… JEE Main 2026Given below are two statements: one is labelled as Assertion (A) and the other is… JEE Main 2026An electron is travelling with a velocity v in free space and when it enters a medium… JEE Main 2026An electron of mass m is moving in an electric field E = -2E_0 i ( E_0 = constant > 0 )… JEE Main 2026Light source having wavelength 331 nm is used to generate photo-electrons whose stopping… JEE Main 2026Match the LIST-I with LIST-II List-I List-II A. Planck's constant I. ML^2T^ -2 B.… JEE Main 2026The de Broglie wavelength associated with an electron accelerated through a potential… JEE Main 2026 Full Dual Nature of Matter list All JEE Main PYQs