The human body has a surface area of approximately $1.8 \mathrm{m}^{2}$, a surface temperature of approximately $30^{\circ} \mathrm{C}$, and a typical emissivity at infrared wavelengths of e = 0.97. If we make the approximation that all photons are emitted at the wavelength of peak intensity, how many photons per second does the body emit?

What would be the wavelengths of the two photons produced when an electron and a positron, each with $420 \mathrm{keV}$ of kinetic energy, annihilate in a head-on collision?

In the photoelectric effect, electrons are ejected from the surface of a metal when light shines on it. Which one or more of the following would lead to an increase in the maximum kinetic energy of the ejected electrons? (a) Increasing the frequency of the incident light (b) Increasing the number of photons per second striking the surface (c) Using photons whose frequency $f_{0}$ is less than $W_{0} / h$ is the work function of the metal and his Planck's constant (d) Selecting a metal that has a greater work function

Calculate the energies of photons related to the two lines using the relationships expressed in the following equations. $E_{\text {photon }}=h v ; c=\lambda v ; E=h c / \lambda$

Estimate the number of photons emitted per second from $1.0 \mathrm{cm}^{2}$ of a person’s skin if a typical emitted photon has a wavelength of 10,000 nm.

How many $550 \mathrm{~nm}$ photons would have to be absorbed to raise the temperature of $1.0 \mathrm{~g}$ of water by $1.0^{\circ} \mathrm{C}$ ?

What are the literal and symbolic meanings of each character or object from the allegory? Use a chart like this one to record your answers.

A pulsed ruby laser emits light at 694.3 nm. For a 14.0-ps pulse containing 3.00 J of energy, find the number of photons in it.

Simplify. $\left(-2 w^3 z^4\right)^3\left(-4 w z^3\right)^2$

In Exercises, use a symbolic differentiation utility to analyze the graph of the function. Label any extrema and/or asymptotes that exist.

$f(x)=\frac{x^2}{x^2-1}$

How much energy (in kj) do 3.0 moles of photons, all with a wavelength of 670 nm, contain?

Identify each quantity as either a scalar or a vector. Explain. (a) muzzle velocity of a bullet, (b) price of a company’s stock, (c) air temperature of a room, (d) weight of an automobile, (e) volume of a fish tank, (f ) current of a river.

When a hydrogen atom is in its ground state, what are the shortest and longest wavelengths of the photons it can absorb without being ionized?

A random sample of $n=100$ measurements has been selected from a population with unknown mean $\mu$ and known standard deviation $\sigma=10$. Calculate the width of the confidence interval for $\mu$ for the confidence levels given in the exercise. What effect do the changing confidence levels have on the width of the interval? $99 \%(\alpha=.01)$