Answer
A.
(i), (iii)
According to Einstein photoelectric equation,
E = Kmax + ϕ
h cλ = ϕ + eVs
∴ Vs = hcλ - ϕ 1e
Vs versus 1λ graph is a straight line.
Slope
tanθ = h ce
The curves intersect the 1λ axis, where Vs is zero
∴ h cλ - ϕ = 0
⇒ 1λ = ϕh c
For metal 1
ϕ1h c = 0.001
For metal 2
ϕ2hc = 0.002
For metal 3
ϕ3hc = 0.004
∴ ϕ1 : ϕ2 : ϕ3 = 1 : 2 : 4
For metal 1
λO1 = hcϕ = 10.001 = 1000 nm
For metal 2, threshold wavelength,
λO2 = hcϕ = 10.002 = 500 nm
Simillarly,
λO3 = hcϕ = 10.004 = 250 nm
λvoilet = 400 nm
For metal 1
λvoilet < λthreshold
For metal 3
λvoilet > λthreshold
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- Metal 1 may be gold and metal 2 may be cesium
- θ1 > θ2, if metal -1 is gold and metal -2 is cesium
- θ1 = θ2 for any two metals
- θ1 > θ2, if metal -1 and metal -2 are gold and copper respectively