Radiations of monochromatic waves of wavelength are made incident on the surface of metals with work functions ϕ1​ and ϕ2​ respectively (take λ as the wavelength). Which of the following relationships holds true?
(a) ϕ1​=ϕ2​
(b) ϕ1​>ϕ2​
(c) ϕ1​<ϕ2​
(d) ϕ1​=ϕ2​+λ