JEE Main & Advanced Sample Paper JEE Main Sample Paper-43

  • question_answer
    A 60 W bulb is placed at a distance of 4 m from you. The bulb is emitting light of wavelength 600 nm uniformly in all directions. In 0.1 s, how many photons enter your eye if the pupil of the eye is having a diameter of 2 mm? [Take, he =1240 eV-nm]

    A)  \[2.84\times {{10}^{12}}\]             

    B)  \[2.84\times {{10}^{11}}\]

    C)  \[9.37\times {{10}^{11}}\]             

    D)  \[6.48\times {{10}^{11}}\]

    Correct Answer: A

    Solution :

     The intensity of light of the location of your eye is \[\Rightarrow \] The energy entering into your eye per second is \[\omega =\frac{3v}{4l}\] Where d is diameter of pupil \[T=2\pi \,\sqrt{\frac{L}{g}}\] \[\frac{L}{2}\] Let \[\Rightarrow \] be the number of photons entering into the eye per sec, then \[T=2\pi \sqrt{\frac{L}{2g}}\] \[\Rightarrow \] \[M=(AL)d\,\,\,\Rightarrow \,\,\frac{M}{Ad}\] \[\Rightarrow \] \[T=2\pi \,\,\sqrt{\frac{M}{2Adg}}\] photons/s So, the number of photons entering the eye in 0.1 s, is \[\Delta DBS,\].

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