The human eye can barely detect a yellow lings (`lamda=6000A`) that delivers `1.7xx10^(-18)`W to the retina. The number of photons per second falling on the eye is nearest to

Photons of wavelength lamda=662 nm are incident normally on a perfectly reflecting screen. Calculate their number of photons per second falling on the screen such that the exerted force is 1 N.

The sun gives light at the rate of 1400Wm^(-2) of area perpendicular to the direction of light. Assume lamda(sunlight)=6000A . Calculate A.the number of photons per second arriving at 1 m^2 area at earth. B. the number of photons emitted from the sun per second assuming the average radius of the Earth's orbit is 1.49xx10^(11) m.

The sun gives light at the rate of 1400Wm^(-2) of area perpendicular to the direction of light. Assume lamda(sunlight)=6000A . Calculate A.the number of photons per second arriving at 1 m^2 area at earth. B. the number of photons emitted from the sun per second assuming the average radius of the Earth's orbit is 1.49xx10^(11) m.

The sun gives light at the rate of 1400Wm^(-2) of area perpendicular to the direction of light. Assume lamda(sunlight)=6000A . Calculate A.the number of photons per second arriving at 1 m^2 area at earth. B. the number of photons emitted from the sun per second assuming the average radius of the Earth's orbit is 1.49xx10^(11) m.

Estimating the following number should be interesting. The number tells you why our eye can never 'count photons', even in barely detectable light. The number of photons entering the pupil of our eye per second corresponding to the minimum intensity of white light that we humans can perceive (~10^(-10) W. m^(-2)) . Take the area of the pupil to be about 0.4 cm^(2) and the average frequency of the white light to be about 6xx10^(14) Hz.

Eye of an experimenter detects the green light (lambda =5000 Å) at 5xx10^4 photons per square meter per second and ear can detect 10^-13 watt per square metre. The eye is sensitive as a power detector in comparison to the ear by a factor of

A normal human eye can detect yellow light if more than 10 photons enter into it per second. A star is generating as much power as the Sun and is emitting predominantly yellow light (lambda = 6000 Å) . How far is the star if our eye isbarely able to see it? It is given that intensity of solar light on surface of the earth is I = 1400 Wm^(– 2) and the distance of the Sun from the Earth is r = 1.5 × 10^(11) m . The diameter of pupil of our eye is d = 6 mm .