# Physics: Hydrogen alpha, internal reflection, focal length, refraction, Snell's Law

Turn in your answers to the following problems below. As always, make sure to show all of your work.

1. The so-called "hydrogen alpha (Ha) line" is a specific wavelength of red light caused by excited atomic hydrogen. It is frequently used when studying the Sun. The wavelength of Ha is 656.3 nm, or 656.3*10-9 m. The speed of light in vacuum is 3*108 m/s. What is the frequency ( in units of cycles per second, or 1/s) of Ha in vacuum?

2. Light is incident at angle A from a media with n = 1.5 to one with n = 2.0 as shown in the figure. What is the minimum value for A so that there is total internal reflection at point P, which is at the interface between the n = 2 and n = 1 materials?

3. An object of height 5 cm is placed 30 cm in front of spherical concave mirror. If the image is real and 10 cm high, what is the radius of curvature of the mirror?

4. Two lenses are placed on the x-axis. The first lens is a diverging lens with focal length 4cm placed at x = -2cm. The second lens is a converging lens with focal length 7cm placed at x = 8cm. If an object is placed at x = -18cm, what is the position of the image on the x-axis? (Find the answer to the nearest centimeter)

5. In the above problem, which of the following characterizes the final image when compared to the original object?

a. Correctly oriented.

b. Upside down.

c. Backwards (right to left reversal).

d. Upside down and backwards.

https://brainmass.com/physics/light-refraction/hydrogen-alpha-internal-reflection-focal-length-refraction-301378

#### Solution Summary

Hydrogen alpha, internal reflection, focal length, refraction, and Snell's Law are discussed.