Question

The work function for aluminium surface is 4.2 eV and that for sodium surface is 2.0 eV. The two metals were illuminated with appropriate radiations so as to cause photo emission. Then :

• A. Both illuminated and sodium will have them same threshold frequency
• B. The threshold frequency of aluminium will be more than that of sodium
• C. The threshold frequency of aluminium will be less than that of sodium
• D. The threshold wavelength of aluminium will be more than that of sodium

Answer 1

Answer: (B)

The threshold frequency of aluminium will be more than that of sodium

$w_0=h{v}_0,$ thus the greater work function, the higher is the threshold frequency and hence the lower is the threshold wavelength.