The intensity of the Sun's light in the vicinity of the earth is about `1000 W//m^2` .Imagine a spacecraft with a mirrored square sail of dimension 1.0 km. Estimate how much thrust (in newtons) this crafts will experience due to collisions with the Sun's photons

Intensity of sunlight on the surface of the earth is I = 1400 W//m^(2) (neglecting atmospheric absorption). (a) Find the Wattage of the Sun. (b) Assuming that light emitted from the sun is monochromatic having wavelength l = 6000 Å , estimate the number of photons emitted from the sun in one second. (c) According to mass energy equivalence principle, estimate the decrease in mass of the sun in one second. Given: h = 6.64 xx 10^(-34) Js, c = 3 xx 10^(8) m//s

Solar constant, I_(s) is defined as intensity of solar radiation incident on the Earth. Its value is close to 1.4 kW//m^(2) . Nearly 68% of this energy is absorbed by the Earth. The average temperature of Earth is about 290 K. Radius of the Earth is R_(e) = 6000 km and that of the Sun is R_(s) = 700,000 km . Earth - Sun distance is r = 1.5 xx 10_(8) km . Assume Sun to be a black body. (a) Estimate the effective emissivity of earth. (b) Find the power of the sun. (c) Estimate the surface temperature of the Sun.

Define the term 'intensity of radiation in photon picture of light. Ultraviolet light of wavelength 2270Å from 100W mercury source irradiates a photo cell made of a given metal. If the stopping potential is -1.3V, estimate the work function of the metal. How would the photon cell respond to a high intensity (~10^(5) W.m^(-2)) red light of wavelength 6300Å produced by a laser?

Consider a 20W bult emitting light of wavelength 5000Å and shinning on a metal surface kept at a distance 2m. Assume that the metal surface has work function of 2eV and that each atom on the metal surface can be treated as a circular disk of radius 1.5Å. (i) Estimate no. of photons emitted by the bulb per second. [Assume no other losses] (ii) Will there be photoelectric emission? (iii) How much time would be required by the atomic disk to receive energy equal to work function (2eV)? (iv) How many photons would atomic disk receive within time duration calculated in (iii) above? (v) Can you explain how photoelectric effect was observed instantaneously? [Hing : Time calculated in part (iii) is from classical consideration and you may further take the target of surface area say 1cm^(2) and estimate what would happen?]

When the sun is directly overhead, the surface of the earth receives 1.4 xx (10^3) W (m^-2) of sunlight. Assume that the light is monochromatic with average wavelength 500mn and that no light is absorbed in between the sun and the earth's surface. The distance between the sun and the earth is 1.5 xx (10^11) m. (a) Calculate the number of photons falling per second on each square metre of earth's surface directly below the sun. (b) How many photons are there in each cubic metre near the earth's surface at any instant? (c) How many photons does the sun emit per second?

When the sun is directly overhead, the surface of the earth receives 1.4 xx (10^3) W (m^-2) of sunlight. Assume that the light is monochromatic with average wavelength 500mn and that no light is absorbed in between the sun and the earth's surface. The distance between the sun and the earth is 1.5 xx (10^11) m. (a) Calculate the number of photons falling per second on each square metre of earth's surface directly below the sun. (b) How many photons are there in each cubic metre near the earth's surface at any instant? (c) How many photons does the sun emit per second?

When the sun is directly overhead, the surface of the earth receives 1.4 xx (10^3) W (m^-2) of sunlight. Assume that the light is monochromatic with average wavelength 500mn and that no light is absorbed in between the sun and the earth's surface. The distance between the sun and the earth is 1.5 xx (10^11) m. (a) Calculate the number of photons falling per second on each square metre of earth's surface directly below the sun. (b) How many photons are there in each cubic metre near the earth's surface at any instant? (c) How many photons does the sun emit per second?