WHAT IS NASA PHYSICS?
Forces and Motion
Conservation of Momentum & Energy
Temperature and Heat
Anticipation Guide 7
Intro to Modern Physics
The Ultraviolet Catastrophe
The Photoelectric Effect
Special Relativity (SR)
Distance and Time
May the Forces be with You
Modern Physics Notebook
Assessment Problems 7
The Speed of Light
Wavelength and Frequency
Light and Objects
1. The speed of light is about 3.0 x 108 m/s. How far will light travel in 1 year?
Answer: We need to determine the number of seconds in a year.
(1 year)(365 days/year)(24 hr/day)(60 minutes/hr)(60 sec/min) = 3.15 x 107 seconds.
Then, (3.0 x 108 m/s)(3.15 x 107 s) = 9.5 x 1015 m.
2. A portion of the electromagnetic spectrum emits radiation with a frequency ν and has a wavelength, λ. What would be the wavelength of radiation with frequency 2ν?
Answer: Since c = νλ and c is the speed of light, a constant, then doubling the frequency would require that the wavelength be halved or be expressed as λ/2.
3. An electromagnetic wave has a frequency of 9.6 x 1014 Hz. What is its wavelength? (One Hz equals one cycle per second or 1/s.)
Answer: c = νλ Then, λ = c/ν and λ = 3.0 x 108 m/s/9.6 x 1014 1/s = 3.1 x 10-7 m.
4. Is the wave in problem 3 in the visible portion of the electromagnetic spectrum, the infrared or the ultraviolet? (The range of wavelengths in the visible portion of the electromagnetic spectrum range from about 3.8 x 10-7 m to 7.5 x 10-7 m.)
Answer: Since the wavelength in problem 3 is 3.1 x 10-7 m and therefore shorter than the shortest wavelength in the visible portion of the visible spectrum, the wave would be in the ultraviolet region