Exams › JEE Main › Physics

What is the ratio of the de Broglie wavelengths of electrons that are accelerated from rest through potential differences of 100 V, 200 V, and 300 V, respectively?

1. 1: 2: 3
2. 1: 4: 9
3. 1: 1/√2: 1/√3
4. 1: 1/2: 1/3

Correct answer: 1: 1/√2: 1/√3

Solution

de Broglie wavelength lambda = h/sqrt(2meV) so lambda ~ 1/sqrt(V). For 100, 200, 300 V the ratio is 1 : 1/sqrt(2) : 1/sqrt(3).

Related JEE Main Physics questions

• A star is sending out light of wavelength 5000 Å and is moving toward the Earth with a speed of 1.50 × 10⁶ m/s. What is the shift in the wavelength of the light observed on Earth?
• A beam of radiation carrying energy E is incident perpendicularly on a perfectly reflecting surface. What momentum is imparted to the surface? (C = speed of light)
• Two identical photocathodes are illuminated by light of frequencies f1 and f2. If the emitted photoelectrons have speeds v1 and v2 respectively, then
• An X-ray tube is run with a potential difference of 15 kV. What is the maximum possible speed of the electrons that hit the target?
• In a photoelectric setup, monochromatic light of wavelength λ ejects electrons, and the maximum speed of the emitted electrons is v. If the incident wavelength is changed to 5λ/4, the speed of the emitted electrons will be
• A sodium street lamp rated at 200 W produces yellow radiation of wavelength 0.6 μm. If only 25% of the electrical power is converted into light, how many yellow photons are emitted each second?

⚔️ Practice JEE Main Physics free + battle 1v1 →