KCET · Physics · Dual Nature of Matter
The number of photons falling per second on a completely darkened plate to produce a force
of \( 6.62 \times 10^{-5} \mathrm{~N} \) is ' \( n \) '. If the wavelength of the light falling is \( 5 \times 10^{-7} \mathrm{~m} \), then \( n= \)
\( \times 10^{22} \).
\( \left(h=6.62 \times 10^{-34}\right) \mathrm{J}_{\mathrm{S}} \)
- A \( 11 \)
- B \( 05 \)
- C \( 0.2 \)
- D \( 3.3 \)
Answer & Solution
Correct Answer
(B) \( 05 \)
Step-by-step Solution
Detailed explanation
Given, force, \(F=6.62 \times 10^{-5} \mathrm{~N} ;\) wavelength,\(\lambda=5 \times 10^{-7} \mathrm{~m}\)
Now, \(C \times F=\frac{h c}{\lambda} \times \frac{n}{t}\)
or \(F=\frac{h n}{\lambda t}\)
\(\Rightarrow \frac{n}{t}=\frac{F \lambda}{h}=\frac{6.62 \times 10^{-5}}{6.62 \times 10^{-34}} \times 5 \times 10^{-7}=5 \times 10^{22}\)
Therefore, number of photons falling per second \(=5 \times 10^{22}\)
Now, \(C \times F=\frac{h c}{\lambda} \times \frac{n}{t}\)
or \(F=\frac{h n}{\lambda t}\)
\(\Rightarrow \frac{n}{t}=\frac{F \lambda}{h}=\frac{6.62 \times 10^{-5}}{6.62 \times 10^{-34}} \times 5 \times 10^{-7}=5 \times 10^{22}\)
Therefore, number of photons falling per second \(=5 \times 10^{22}\)
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Physics
- Two particles of masses \( m_{1} \) and \( m_{2} \) have equal kinetic energies. The ratio of their momentum isKCET 2018 Easy
- An electron enters the space between the plates of a charged capacitor as shown. The charge density on the plate is \(\sigma\). Electric intensity in the space between the plates is E. A uniform magnetic field \(B\) also exists in the space perpendicular to the direction of \(E\)
The electron moves perpendicular to both \(\overrightarrow{\mathrm{E}}\) and \(\overrightarrow{\mathbf{B}}\) without any change in direction. The time taken by the electron to travel a distance \(l\) in the space is
KCET 2010 Hard - Which of the following expression can be deduced on the basis of dimensional analysis? (All symbols have their usual meanings)KCET 2025 Medium
- A current of \(2 \mathrm{~A}\) is passing through a metal wire of cross-sectional area \(2 \times 10^{-6} \mathrm{~m}^{2}\). If the number density of free electrons in the wire is \(5 \times 10^{26} \mathrm{~m}^{-3}\), the drift speed of electrons is (Given, \(\mathrm{e}=1.6 \times 10^{-19} \mathrm{C}\) )KCET 2012 Medium
- A door \(1.6 \mathrm{~m}\) wide requires a force of \(1 \mathrm{~N}\) to be applied at the free end to open or close it. The force that is required at a point \(0.4 \mathrm{~m}\) distance from the hinges for opening or closing the door isKCET 2009 Medium
- Identify the correct statementKCET 2025 Easy
More PYQs from KCET
- The shaded region in the figure is the solution set of the inequations
KCET 2019 Easy - An electromagnetic wave is travelling in \( x \)-direction with electric field vector given by, \( \vec{E}_{y}=E_{0} \sin (k x-\omega t) \hat{j} \). The correct expression for magnetic field vector isKCET 2019 Easy
- A member of the Lanthanoid series which is well known to exhibit +4 oxidation state isKCET 2025 Easy
- If \(A=\left[\begin{array}{cc}2-k & 2 \\ 1 & 3-k\end{array}\right]\) is singular matrix, then the value of \(5 k-k^2\) is equal toKCET 2023 Easy
- Mercury is a liquid metal becauseKCET 2008 Easy
- A row matrix has onlyKCET 2026 Easy