Radiation, with wavelength 6561 A falls on a metal surface to produce photoelectrons. The electrons are made to enter a uniform magnetic field of 3×10⁻⁴ T. If the radius of the largest circular path followed by the electrons is 10 mm, the work function of the metal is close to

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(2) 1.1 eV. Given: λ=6561 A, B=3×10⁻⁴ T, r=10⁻² m. v=(eBr)/m=(1.6×10⁻¹⁹×3×10⁻⁴×10⁻²)/(9.1×10⁻³¹)=5.3×10⁵ m s⁻¹. K=1/2 mv²=1.26×10⁻¹⁹ J =0.79 eV. E=(12400)/(6561)=1.89 eV, so φ=1.89-0.79≈1.1 eV.

Radiation, with wavelength 6561 A falls on a metal surface to produce photoelectrons. The electrons are made to enter a uniform magnetic field of 3×10⁻⁴ T. If the radius of the largest circular path followed by the electrons is 10 mm, the work function of the metal is close to

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