Question

let me answer with explanation immediately please

Answer 1

Hey here is your answer its the formula so your answer will be 3100 A in second pic you can see

Answer 2

From Photon theory of photoelectric effect
-------------------------------------------------------------

K.E = hf _ phi (phi means work function ) ---------------(1)

Given data :-
----------------

1▪ Work function = phi = 4eV

As one electron is equal to 1.6 × 10^_19

So

Work function = phi = 4 ×1.6 ×10^_19V

Work function =phi= 6.4×10^_19V

2▪ Velocity is given which is equal to zero

Now

K.E = hf _ phi

We know that kinetic energy = 1/2 mv^2

As v = 0

So

K.E =1/2mv^2

K.E = 1/2 m (0)^2

K.E = 0 ---------------(a)

hf = hc/lemda (as f=c/lemda) --------------(b)

Put a and b in equation 1

0 = hc/lemda _ phi

phi = hc/lemda

lemda = hc/phi

h is planck constant = 6.62×10^_34 Js

c is speed of light = 3×10^8m/s

lemda = 6.62×10^_34 ×3 ×10^8 / 6.4 ×10^_19

lemda = 19.86 ×10^_34+8 / 6.4×10^_19

lemda = 19.86 ×10^_26 / 6.4×10^_19

lemda = 3.103 × 10^_26+19

lemda = 3.103 ×10^_7 m

SO

Wavelength is equal to 3.103 ×10^_7 m

_____________________

INSHALLAH IT WILL HELP U

HAVE A NICE DAY☺☺☺☺