The intensity of solar radiation at the top of the Earth’s atmosphere is 1 370 W/m2. Assuming 60% of the incoming solar energy reaches the Earth’s surface and you absorb 50% of the incident energy, make an order-of-magnitude estimate of the amount of solar energy you absorb if you sunbathe for 60 minutes.

The energy from solar radiation falling on Earth is

$$1.07 \times 10 ^ { 16 } \mathrm { kJ } / \mathrm { min }$$

lf the energy released in the reaction

$$^ { 235 } \mathrm { U } + _ { 0 } ^1 \mathrm { n } \longrightarrow _ { 56 } ^ { 141 } \mathrm { Ba } + _ { 36 } ^ { 92 } \mathrm { Kr } + 3 _ { 0 } ^ { 1 } \mathrm { n }$$

(

$$^{235}U$$

nuclear mass, 234.9935 amu;

$$^{141} Ba$$

nuclear mass, 140.8833 amu;

$$^{92}Kr$$

nuclear mass, 91.9021 amu) is taken as typical of that occurring in a nuclear reactor, what mass of uranium-235 is required to equal 0.10% of the solar energy that falls on Earth in 1.0 day?

A pulsed ruby laser emits light at 694.3 nm. For a 14.0-ps pulse containing 3.00 J of energy, find (a) the physical length of the pulse as it travels through space and (b) the number of photons in it. (c) Assuming that the beam has a circular cross section of 0.600 cm diameter, find the number of photons per cubic millimeter.

Assume that the solar radiation incident on Earth is $1340 \mathrm{~W} / \mathrm{m}^2$ (at the top of Earth's atmosphere). Calculate the total power radiated by the Sun, taking the average separation between Earth and the Sun to be $1.49 \times 10^{11} \mathrm{~m}$.

Solar radiation is incident at the earth’s surface at an average of $1000 \ \mathrm {W/ m ^{2}}$ on a surface normal to the rays. For a mean wavelength of $550$ nm, calculate the number of photons falling on $1\ \mathrm {cm}^2$ of the surface each second.

When the sun is high in the sky, it delivers approximately 1000 watts of power to each square meter of earth's surface. The temperature of the surface of the sun is about 6000 K, while that of the earth is about 300 K. (a) Estimate the entropy created in one year by the flow of solar heat onto a square meter of the earth. (b) Suppose you plant grass on this square meter of earth. Some people might argue that the growth of the grass (or of any other living thing) violates the second law of thermodynamics, because disorderly nutrients are converted into an orderly life form. How would you respond?

The intensity of solar radiation at the top of the Earth's atmosphere is $1340 \mathrm{~W} / \mathrm{m}^2$. Assuming that $60 \%$ of the incoming solar energy reaches the Earth's surface and assuming that you absorb $50 \%$ of the incident energy, make an order-of-magnitude estimate of the amount of solar energy you absorb in a 60-min sunbath.

The intensity of solar radiation at the top of the Earth's atmosphere is $1370 \mathrm{W} / \mathrm{m}^{2}$. Assuming 60% of the incoming solar energy reaches the Earth's surface and you absorb 50% of the incident energy, make an order-of-magnitude estimate of the amount of solar energy you absorb if you sunbathe for 60 minutes.

Four different rooms are losing energy to the outside through a wall.The temperature difference between the inside and the outside of the rooms is the same. Which combination of wall area and wall thickness results in the smallest rate of heat loss?

$$\begin{array} { | c | c | c | } \hline & { \text { Area } } & { \text { Thickness } } \\ \hline \mathbf { A } & { S } & { d } \\ \hline \mathbf { B } & { 2 S } & { \frac { d } { 2 } } \\ \hline \mathbf { C } & { S } & { 2 d } \\ \hline \mathbf { D } & { 2 S } & { 2 d } \\ \hline \end{array}$$

A star explodes in the vacuum of space. The thermal energy transferred by the star takes place through: A. radiation B. conduction C. convection D. evaporation

Write expressions for the electric and magnetic fields of a sinusoidal plane electromagnetic wave having an electric field amplitude of 300 V/m and a frequency of 3.00 GHz and traveling in the positive x direction.

A microwave source produces pulses of 20.0-GHz radiation, with each pulse lasting 1.00 ns. A parabolic reflector with a face area of radius 6.00 cm is used to focus the microwaves into a parallel beam of radiation. The average power during each pulse is 25.0 kW. What is the wavelength of these microwaves?

The given figure shows portions of the energy-level diagrams of the helium and neon atoms. An electrical discharge excites the He atom from its ground state (arbitrarily assigned the energy $E_1=0$ ) to its excited state of $20.61 \mathrm{eV}$. The excited He atom collides with a $\mathrm{Ne}$ atom in its ground state and excites this atom to the state at $20.66 \mathrm{eV}$. Lasing action takes place for electron transitions from $E_3{ }^*$ to $E_2$ in the Ne atoms. From the data in the figure, show that the wavelength of the red $\mathrm{He}-\mathrm{Ne}$ laser light is approximately $633 \mathrm{~nm}$.

A dish antenna having a diameter of 20.0 m receives (at normal incidence) a radio signal from a distant source. The radio signal is a continuous sinusoidal wave with amplitude $E_{\max }=0.200 \mu$V/m. Assume the antenna absorbs all the radiation that falls on the dish. What is the power received by the antenna?