AI Mentor

Check Your IQ

Free Expert Demo

Try Test

Courses

Dropper NEET Course Dropper JEE Course Class - 12 NEET Course Class - 12 JEE Course Class - 11 NEET Course Class - 11 JEE Course Class - 10 Foundation NEET Course Class - 10 Foundation JEE Course Class - 10 CBSE Course Class - 9 Foundation NEET Course Class - 9 Foundation JEE Course Class -9 CBSE Course Class - 8 CBSE Course Class - 7 CBSE Course Class - 6 CBSE Course

Offline Centres

A photon with an energy of $4.9 e V$ ejects photoelectrons from tungsten. When the ejected electron enters a constant magnetic field of strength $B = 2.5 m T$ at an angle of $60 °$ with the field direction, the maximum pitch of the helix described by electron is found to be $2.7 m m$ . Find the work function of the metal in electron-volts. Given that specific charge of electron is $1.76 \times 10^{11} C k g^{- 1}$ .

see full answer

Your Exam Success, Personally Taken Care Of

1:1 expert mentors customize learning to your strength and weaknesses – so you score higher in school , IIT JEE and NEET entrance exams.

An Intiative by Sri Chaitanya

$4.5 e v$

$4 e v$

$6.5 e v$

$6 e v$

answer is B.

(Unlock A.I Detailed Solution for FREE)

Best Courses for You

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Detailed Solution

Pitch of helical path is

$p = (v \cos θ) T = \frac{v T}{2}$

$\{∵ θ = 60 °\}$

where, $T = \frac{2 π m}{q B} = \frac{2 π}{B α}$ $\{∵ α = \frac{q}{m}\}$

$\Rightarrow p = \frac{π v}{B α}$

$\Rightarrow v = \frac{B α p}{π}$

$\Rightarrow v = \frac{(2.5 \times 10^{- 3}) (1.76 \times 10^{11}) (2.7 \times 10^{- 3})}{3.14}$

$\Rightarrow v = 3.78 \times 10^{5} {ms}^{- 1}$

Since, $K E = \frac{1}{2} m v^{2} = E - ϕ_{0}$

$\Rightarrow ϕ_{0} = E - \frac{1}{2} m v^{2}$

Substituting value of (v) from equation (1) in equation (2), we get

$ϕ_{0} = 4.9 - \frac{1}{2} \frac{(9.11 \times 10^{- 31}) {(3.78 \times 10^{5})}^{2}}{1.6 \times 10^{- 19}}$

$\Rightarrow ϕ_{0} = (4.9 - 0.4) e V$

$\Rightarrow ϕ_{0} = 4.5 e V$

Watch 3-min video & get full concept clarity

courses

No courses found

Result Producing online coaching for JEE/NEET of south India

Largest All India Test Series for JEE/NEET

Best Online Course for IIT JEE

Best Online Course for NEET

Best Online Course for CBSE

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Get Expert Academic Guidance – Connect with a Counselor Today!