1) The frequency of incident radiation was kept constant.
2) de Broglie wavelength,
\(\lambda =\frac { h }{ \sqrt { 2mqV } } \alpha \frac { 1 }{ V } \)
If potential difference V is doubled, the de-Broglie wavelength is decreased to \(\frac { 1 }{ \sqrt { 2 } } \) time.

Metal A
Since work function W = hv_o
and v_o > V_o so work function of metal A is more.
Aliter :
On stopping potential axis \(-\frac { { W }_{ o }^{ ' } }{ e } >-\frac { { W }_{ o } }{ e } \)
Hence work function W'o of metal A is more.

we know,
de Broglie wavelength,
\(\lambda =\frac { h }{ p } =\frac { h }{ mv } \Rightarrow \lambda \alpha \frac { 1 }{ v } \)
Also \(v\alpha \frac { 1 }{ n } \)
\(\lambda \alpha n\)
∴ de Broglie wavelength will increase

Laws of photoelectric effect:
(i) For a given surface, the emission of photoelectrons takes place only if the frequency of incident light is greater than a certain minimum frequency called the threshold frequency.
(ii) For a given frequency of incident light, the number of photoelectrons emitted is directly proportional to the intensity of the incident light. The saturation current is also directly proportional to the intensity of incident light.
(iii) Maximum kinetic energy of the photoelectrons is independent of the intensity of the incident light.
(iv) Maximum kinetic energy of the photoelectrons from a given metal is directly proportional to the frequency of incident light.
(v) There is no time lag between the incidence of light and the ejection of photoelectrons.