Two identical photo cathodes receive light of frequencies f1 and f2. if the velocities of the photoelectrons (of mass m) coming out are respectively v1 and v2, then

Question

Two identical photo cathodes receive light of frequencies f1 and f2. if the velocities of the photoelectrons (of mass m) coming out are respectively v1 and v2, then (A) v21-v22=(2h/m)(f1-f2) (B) v1+v2=[(2h/m)(f1+f2)]1/ 2 (C) v21-v22=(2h/m)(f1+f2) (D) v1-v2=[(2h/m)(f1-f2)]1/ 2

Tardigrade Admin · Accepted Answer

(1/2)m(v21-v22)=h(f1-f2) ⇒ v21-v22=(2h/m)(f1-f2).

Q. Two identical photo cathodes receive light of frequencies $f_{1}$ and $f_{2}$ . if the velocities of the photoelectrons (of mass m) coming out are respectively $v_{1}$ and $v_{2}$ , then

$v_{1}^{2} - v_{2}^{2} = \frac{2 h}{m} (f_{1} - f_{2})$

$v_{1} + v_{2} = [\frac{2 h}{m} (f_{1} + f_{2})]^{1/2}$

$v_{1}^{2} - v_{2}^{2} = \frac{2 h}{m} (f_{1} + f_{2})$

$v_{1} - v_{2} = [\frac{2 h}{m} (f_{1} - f_{2})]^{1/2}$

$\frac{1}{2} m (v_{1}^{2} - v_{2}^{2}) = h (f_{1} - f_{2})$
$\Rightarrow v_{1}^{2} - v_{2}^{2} = \frac{2 h}{m} (f_{1} - f_{2}) .$

Q. Two identical photo cathodes receive light of frequencies f1​ and f2​. if the velocities of the photoelectrons (of mass m) coming out are respectively v1​ and v2​, then

v12​−v22​=m2h​(f1​−f2​)

v1​+v2​=[m2h​(f1​+f2​)]1/2

v12​−v22​=m2h​(f1​+f2​)

v1​−v2​=[m2h​(f1​−f2​)]1/2