If a light bulb manufacturing company wants to estimate, with 95% confidence, the mean life of light emitting diode (LED) light bulbs to within $\pm$ 400 hours and also assumes that the population standard deviation is 1,500 hours, how many LED light bulbs need to be selected?

One light-year is defined by astronomers to be the distance that a beam of light will travel in 1 year (365 days). If the speed of light is 186,000 miles per second, how many miles are in a light-year? Express your answer in scientific notation.

Given that the speed of light equals $3.0 \times 10^8 \mathrm{~m} / \mathrm{s}$ and the wavelength of light is $389 \mathrm{~nm}\left(389 \times 10^{-9} \mathrm{~m}\right)$, calculate the frequency of the light.

Describe the detection of light.

How does light from a laser differ from light from an ordinary lamp?

A traffic light at an intersection is hanging from two wires of equal length at $15^{\circ}$ below the horizontal. If the traffic light weighs 560 pounds, what is the tension in each wire keeping the light at equilibrium?

A light year is approximately 6,000,000,000,000,000 mi. Describe a light year using Ym (yottameters).

Red light has a longer wavelength than violet light. Which has the greater frequency?

Fields cannot travel faster than the speed of light. List some examples of fields that travel slower than the speed of light and fields that travel at the speed of light.

The wavelength of some violet light is $420.0 \text{ nm}$. What is the frequency of this violet light?

The average diameter of the Milky Way galaxy is about 115,000 light-years. Which choice below correctly expresses this in scientific notation? (1)

$$1 \times 10 ^ { 5 } \text { light-years }$$

(2)

$$115 \times 10 ^ { 5 } \text { light-years }$$

(3)

$$1.15 \times 10 ^ { 5 } \text { light-years }$$

(4)

$$2.3 \times 10 ^ { 10 } \text { light-years }$$

Complete the sentence in a way that shows you understand the meaning of the italicized vocabulary word.

Celerity of work was important to the construction crew because ...

Choose the best answer to given of the following. Explain your reasoning with one or more complete sentence.
Why is a sunflower yellow?
(a) It emits yellow light.
(b) It absorbs yellow light.
(c) It reflects yellow light.

Use the given information. The number of miles that light travels in one year is called a light-year. One light-year is equal to $5.88\times10^{12}$ miles.

The average distance from the earth to the sun is 93 million miles. Write this number in scientific notation. Use the number of miles in a light-year to find how many minutes it takes light to reach the earth from the sun.