A light beam of wavelength 500 nm is incident on a metal having work function of 1.25 eV, placed in a magnetic field of intensity B. The electrons emitted perpendicular to the magnetic field B, with maximum kinetic energy are bent into circular arc of radius 30cm. The value of B is __________ x x 10⁻⁷ T
Given hc = 20 × 10?²? J-m, mass of electron = 9 × 10⁻³¹ kg
A light beam of wavelength 500 nm is incident on a metal having work function of 1.25 eV, placed in a magnetic field of intensity B. The electrons emitted perpendicular to the magnetic field B, with maximum kinetic energy are bent into circular arc of radius 30cm. The value of B is __________ x x 10⁻⁷ T
Given hc = 20 × 10?²? J-m, mass of electron = 9 × 10⁻³¹ kg
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1 Answer
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K = hc/λ - W?
K = (20×10? ²? )/ (500×10? ) - 1.25 × 1.6×10? ¹?
K = 4×10? ¹? - 2×10? ¹? = 2×10? ¹? J
R = √ (2mK)/ (eB)
B = √ (2mK)/ (eR) = √ (2 × 9×10? ³¹ × 2×10? ¹? ) / (1.6×10? ¹? × 30×10? ²)
B = √ (36×10? ) / (48×10? ²¹) = (6×10? ²? ) / (4.8×10? ²? ) = 1.25 × 10? T
B = 125 × 10? T
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