A $200\, W$ sodium street lamp emits yellow light of wavelength $0.6 \, \mu m. $ Assuming it to be $25 \% $ efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is
- $1.5 \times 10^{20} $
- $6 \times 10^{18} $
- $62 \times 10^{20} $
- $3 \times 10^{19} $
The Correct Option is A
Solution and Explanation
Power converted to light $P _{1}=200(25 / 100)=50 W$
Energy of photon, $E _{ p }=\frac{ hc }{\lambda}=\frac{6.62 \times 10^{-34} \times 3 \times 10^{8}}{0.6 \times 10^{-6}}=33.1 \times 10^{-20} J$
Thus, $n =\frac{50}{33.1 \times 10^{20}}=1.5 \times 10^{20}$
Top Questions on Dual nature of matter
- Consider a neutron (mass $m$) of kinetic energy $E$ and a photon of the same energy. Let $\lambda_n$ and $\lambda_p$ be the de Broglie wavelength of neutron and the wavelength of photon respectively. Obtain an expression for $\dfrac{\lambda_n{\lambda_p}$.}
- Assam Board Class 12 - 2026
- Physics
- Dual nature of matter
- The waves associated with a moving electron and a moving proton have the same wavelength \( \lambda \). It implies that they have the same :
- Assam Board Class 12 - 2026
- Physics
- Dual nature of matter
- The ratio of de Broglie wavelength of a deuteron with kinetic energy \(E\) to that of an alpha particle with kinetic energy \(2E\) is \(n:1\). (Assume mass of proton \(=\) mass of neutron.) Find the value of \(n\).
- JEE Main - 2026
- Physics
- Dual nature of matter
- The work functions of two metals ($M_A$ and $M_B$) are in the 1 : 2 ratio. When these metals are exposed to photons of energy 6 eV, the kinetic energy of liberated electrons of $M_A$ : $M_B$ is in the ratio of 2.642 : 1. The work functions (in eV) of $M_A$ and $M_B$ are respectively.
- JEE Main - 2026
- Chemistry
- Dual nature of matter
- The equation of the electric field of an electromagnetic wave propagating through free space is given by: \(E = \sqrt{377} \sin(6.27 \times 10^3 t - 2.09 \times 10^{-5} x)\) N/C. The average power of the electromagnetic wave is (1/a) W/m². The value of a is_______. (Take \(\sqrt{\mu_0/\varepsilon_0} = 377\) in SI units)}
- JEE Main - 2026
- Physics
- Dual nature of matter
Questions Asked in NEET exam
- A microscope has an objective of focal length \(f_o = 2\) cm and an eyepiece of focal length \(f_e = 4\) cm. The tube length of the microscope is \(L = 40\) cm. If the distance of distinct vision of eye is \(D = 25\) cm, the magnification in the microscope is:
- NEET (UG) - 2025
- Optical Instruments
- A wire of resistance \(R\) is cut into 8 equal pieces. From these pieces, two equivalent resistances are made by adding four of these together in parallel. Then these two are added in series. The net effective resistance of the combination is:
- NEET (UG) - 2025
- Resistance
Consider a water tank shown in the figure. It has one wall at \(x = L\) and can be taken to be very wide in the z direction. When filled with a liquid of surface tension \(S\) and density \( \rho \), the liquid surface makes angle \( \theta_0 \) (\( \theta_0 < < 1 \)) with the x-axis at \(x = L\). If \(y(x)\) is the height of the surface then the equation for \(y(x)\) is: (take \(g\) as the acceleration due to gravity)
- NEET (UG) - 2025
- Surface Tension
- Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The primary function of the Golgi apparatus is to package the materials made by the endoplasmic reticulum and deliver it to intracellular targets and outside the cell.
Reason (R): Vesicles containing materials made by the endoplasmic reticulum fuse with the cis face of the Golgi apparatus, and they are modified and released from the trans face of the Golgi apparatus.- NEET (UG) - 2025
- Cell Biology
AB is a part of an electrical circuit (see figure). The potential difference \(V_A - V_B\), at the instant when current \(i = 2\) A and is increasing at a rate of 1 amp/second is:
- NEET (UG) - 2025
- Electromagnetic Induction and Inductance
Concepts Used:
Dual Nature of Radiation and Matter
The dual nature of matter and the dual nature of radiation were throughgoing concepts of physics. At the beginning of the 20th century, scientists untangled one of the best-kept secrets of nature – the wave-particle duplexity or the dual nature of matter and radiation.
Electronic Emission
The least energy that is needed to emit an electron from the surface of a metal can be supplied to the loose electrons.
Photoelectric Effect
The photoelectric effect is a phenomenon that involves electrons getting away from the surface of materials.
Heisenberg’s Uncertainty Principle
Heisenberg’s Uncertainty Principle states that both the momentum and position of a particle cannot be determined simultaneously.