help@askiitians.com

+91-87964 74404

Grade 12th passIIT JEE Entrance Exam

A metal surface is illuminated by light of two different wavelengths 248nm and 310nm.The maximum speeds of the photoelectrons corresponding to these wavelengths are U1 and U2 respectively.If the ratio U1 and U2=2:1 and hc=1240eV NM, the work function of material is nearly what?

Anubhav Srivastava

9 Years agoGrade 12th pass

1 Answer

Vikas TU

6 Years ago

Here, a metal surface is illuminated by light of two different wavelengths 248 nm and 310 nm.

Ratio u₁/u₂ = 4/1 [∴ u₁²/u₂² = 16/1]

hc = 1240 eV nm

=> According to the formula of kinetic energy:

KEmax = hc/λ - w

=> By substituting the value in above formula, we get

For light of 248 nm wavelengths:

1/2 mu₁² = hc/μ₁ - w

1/2 mu₁² = 1240/248 - w

1/2 mu₁² = 5ev - w ...(1)

For light of 310 nm wavelengths:

1/2 mu₂² = hc/μ₂ - w

1/2 mu₂² = 1240/310 - w

1/2 mu₂² = 4ev - w ...(2)

=> Dividing eq(1) by eq(2), we get

16 =

16(4-w) = 5 - w

64 - 16w = 5 - w

64 - 5 = 16w - w

59 = 15w

w = 59/15

w = 3.93 eV ≈ 3.9 eV

Thus, the work function of the metal is 3.9 eV.

Let S={x:x belongs to R(√3+√2)^(x^2-4) - (√3-√2)^(x^2-4)=10}. Then n(S) is equal to-

iit jee entrance exam

1 Answer Available

Last Activity: 10 Months ago

My rank is 29k, General, should I opt for any state college cse branch or some Nits in which in which I am getting ECE , chemical, mechanics etc....

iit jee entrance exam

1 Answer Available

Last Activity: 3 Years ago

How is Ranquer Eduzone,comparing, Akash,Fitjee,Resonance,Naryana

iit jee entrance exam

1 Answer Available

Last Activity: 4 Years ago

Can class 9th students study syllabus class of 11th

iit jee entrance exam

3 Answers Available

Last Activity: 4 Years ago

Sum of series 2[n/2] ! [n/2]!/ n! [2Co-2C2+3C2....+[-1]^n[n+1]2Cn] where n is an even positive integer. Kindly provide solution of this question and how to generalise this. How do we know that which expansion will give this?

iit jee entrance exam

1 Answer Available

Last Activity: 4 Years ago

View all Questions