Minimum light intensity that can be perceived by normal human eye is about 10-10Wb m-2 . What is the minimum number of photons of wavelength 660 nm that must enter the pupil in 1 s for one to see the object? Area of cross-section of the pupil is 10-4m2 .

Question

Minimum light intensity that can be perceived by normal human eye is about 10-10Wb m-2 . What is the minimum number of photons of wavelength 660 nm that must enter the pupil in 1 s for one to see the object? Area of cross-section of the pupil is 10-4m2 . (A)  3.3× 102  (B)  3.3× 103  (C)  3.3× 104  (D)  3.3× 105

Tardigrade Admin · Accepted Answer

Intensity, I = 10 - 10 W bm - 2 = 10 - 10 Js - 1 m - 2 . Let the number of- photons required be n. Then, ( nhv / 10 - 4 ) = 10 - 10 Hence, n = 10 - 10 × 10 - 4 / hv = 10 - 14 ( λ / hc ) = ( 10 - 14 × 660 × 10 - 9 / 6.6 × 10 - 34 × 3 × 108 ) = 3.3 × 104

Q. Minimum light intensity that can be perceived by normal human eye is about $1 0^{- 10} Wb m^{- 2}$ . What is the minimum number of photons of wavelength $660 nm$ that must enter the pupil in $1 s$ for one to see the object? Area of cross-section of the pupil is $1 0^{- 4} m^{2}$ .

$3.3 \times 10^{2}$

$3.3 \times 10^{3}$

$3.3 \times 10^{4}$

$3.3 \times 10^{5}$

Q. Minimum light intensity that can be perceived by normal human eye is about 10−10Wbm−2 . What is the minimum number of photons of wavelength 660nm that must enter the pupil in 1s for one to see the object? Area of cross-section of the pupil is 10−4m2 .

3.3×102

3.3×103

3.3×104

3.3×105

Intensity, I = 10−10Wbm−2=10−10Js−1m−2 . Let the number of- photons required be n. Then, 10−4nhv​=10−10 Hence, n=10−10×10−4/hv =10−14hcλ​ =6.6×10−34×3×10810−14×660×10−9​ =3.3×104

Q. Minimum light intensity that can be perceived by normal human eye is about $1 0^{- 10} Wb m^{- 2}$ . What is the minimum number of photons of wavelength $660 nm$ that must enter the pupil in $1 s$ for one to see the object? Area of cross-section of the pupil is $1 0^{- 4} m^{2}$ .

$3.3 \times 10^{2}$

$3.3 \times 10^{3}$

$3.3 \times 10^{4}$

$3.3 \times 10^{5}$