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

At night approximately 500 photons per second must enter an unaided human eye for an object to be seen. A small light bulb emits about $5.00 \times 10^{18}$ photons per second uniformly in all directions. The radius of the pupil of the eye is about $4 \times 10^{- 3}$ meters. What is the approximate maximum distance from which the bulb could be seen ?

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

$2.0 \times 10^{4} m$

$5.0 \times 10^{3} m$

$2.0 \times 10^{5} m$

20 m

answer is B.

(Unlock A.I Detailed Solution for FREE)

Best Courses for You

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Detailed Solution

Photons per area per second at a distance r are $5.00 \times 10^{18} / 4 {πr}^{2}$ . Photons per second entering the eye, radius R is then this times ${πR}^{2}$ . Set this product equal to 500 per second and solve for r. The result is [B].

$\frac{5.00 \times 10^{18}}{4 {πr}^{2}} \times {πR}^{2} = 500$

$\Rightarrow \frac{5.00 \times 10^{18}}{4 {πr}^{2}} \times π \times 16 \times 10^{- 6} = 500$

$\Rightarrow r = 2.0 \times 10^{5} m$

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!