In a photo-emissive cell, with exciting wavelength λ,

In a photo-emissive cell, with exciting wavelength λ, the fastest electron has speed v. If the exciting wavelength is changed to 3λ/4 , the speed of the fastest emitted electron will be

1. (3/4)^1/2. v
2. (4/3)^1/2. v
3. less than (4/3)^1/2. v
4. greater than (4/3)^1/2. v

	1	mv² =	hc	- W₀
	2		λ

or	hc	=	1	mv² + W₀
	λ		2

and	1	mv²₁ =	hc	- W₀
	2		(3λ/4)

	1			1	mv² + W₀		- W₀
	4			2

So, v₁ is greater than

v₁ =		4		^1/2
		3