A satellite in Earth orbit maintains a panel of solar cells of area perpendicular to the direction of the Sun’s light rays. The intensity of the light at the panel is . (a) At what rate does solar energy arrive at the panel? (b) At what rate are solar photons absorbed by the panel? Assume that the solar radiation is monochromatic, with a wavelength of 550 nm, and that all the solar radiation striking the panel is absorbed. (c) How long would it take for a “mole of photons” to be absorbed by the panel?
The rate of arrival of solar energy is given by, P = IA……. (1)
Here, I is the intensity, and A is the area.
The energy E of a photon of wavelength is given by,
Here, h is the Planck’s constant, and c is the speed of light.
Substitute the below values in eq 1.
Therefore, the rate of arrival of solar energy is 3.61 kW.
Substitute the below values in eq. 2. to calculate the energy of the photon.
The expression to calculate the rate at which solar photons are absorbed is given by,
Substitute the below values in eq 3.
Therefore, the rate of absorption of photon by panel is
The expression to calculate the time taken by the mole of photons to be absorbed by the panel is given by,
Substitute the below values in eq 4.
Therefore, the required time is 60.2 s.
Question: For the arrangement of Figs. and , electrons in the incident beam in region 1 have energy and the potential step has a height of . What is the angular wave number in (a) region 1 and (b) region 2 ? (c) What is the reflection coefficient? (d) If the incident beam sends electrons against the potential step, approximately how many will be reflected?
Question: Figure 38-13 shows a case in which the momentum component
of a particle is fixed so that ; then, from Heisenberg’s uncertainty principle (Eq. 38-28), the position x of the particle is completely unknown. From the same principle it follows that the opposite is also true; that is, if the position of a particle is exactly known , the uncertainty in its momentum is infinite. Consider an intermediate case, in which the position of a particle is measured, not to infinite precision, but to within a distance of , where is the particle’s de Broglie wavelength. Show that the uncertainty in the (simultaneously measured) momentum component is then equal to the component itself; that is,. Under these circumstances, would a measured momentum of zero surprise you? What about a measured momentum of ? Of ? Of ?
A 100 W sodium lamp radiates energy uniformly in all directions. (a) At what rate are photons emitted by the lamp? (b) At what distance from the lamp will a totally absorbing screen absorb photons at the rate of ? (c) What is the photon flux (photons per unit area per unit time) on a small screen 2.00 m from the lamp?
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