Aim: How do we explain the electromagnetic spectrum Aim: How do we explain the electromagnetic spectrum? (Introduction to Light)

What is light? Light is an electromagnetic wave that travels at a speed of 3.0 x 108 m/s in a vacuum. Unlike mechanical waves, electromagnetic waves do not require a medium to propagate through.

Electromagnetic Spectrum Since the speed of light in a vacuum is constant, and v =fλ, as the frequency of an electromagnetic wave increases, its wavelength decreases and vice versa.

Visible Light 400nm=700nm

Radio Waves Can be made in lightning or by astronomical objects. Used for satellites, computer networks, radar, communication

Microwaves

Infrared Includes most of the thermal radiation emitted by objects near room temperature. Used for military and civilian purposes like surveillance, night vision, weather forecasting, short ranged wireless communication.

Ultraviolet Light UV light is found in sunlight It is used in black lights, gas charge lamps, and causes some substances to glow

X-ray

Gamma ray Produced by decay of naturally occurring radioisotopes and also from atmospheric interactions with cosmic ray particles.

Problem 1 1. A light wave is an electromagnetic wave that has both an electric and magnetic component associated with it. Electromagnetic waves are often distinguished from mechanical waves. The distinction is based on the fact that electromagnetic waves ______. can travel through materials and mechanical waves cannot b. come in a range of frequencies and mechanical waves exist with only certain frequencies c. can travel through a region void of matter and mechanical waves cannot d. electromagnetic waves cannot transport energy and mechanical waves can transport energy e. electromagnetic waves have an infinite speed and mechanical waves have a finite speed

Problem 2 2. Consider the electromagnetic spectrum as you answer these three questions. Which region of the electromagnetic spectrum has the highest frequency? Gamma Rays b. Which region of the electromagnetic spectrum has the longest wavelength? Radiowaves c. Which region of the electromagnetic spectrum will travel with the fastest speed? All electromagnetic waves travel at the same speed

Problem 3. 3. Consider the visible light spectrum as you answer these two questions. Which color of the visible light spectrum has the greatest frequency? Violet b. Which color of the visible light spectrum has the greatest wavelength? Red

Problems 4 and 5 4. Calculate the frequency of a light wave which has a wavelength of 6.04 x 10-7 m. What color is this wave? v=fƛ 3 x 108 m/s=f(6.04 x 10-7 m) f=4.97 x 1014 Hz Orange Calculate the frequency of a light wave which has a wavelength of 5.50 x 10-7 m. What color is the light? v=fƛ 3 x 108 m/s=f(5.5 x 10-7 m) f=5.45 x 1014 Hz

Problems 6 and 7 6. Calculate the wavelength of an electromagnetic wave which has a frequency of 4 x 1017 Hz. What type of electromagnetic wave is this? X ray v=fƛ 3 x 108 m/s=(4 x 1017 Hz)ƛ ƛ=7.5 x 10-10 m 7. Calculate the wavelength of an electromagnetic wave that has a frequency of 5 x 108 Hz. How far will this wave travel in 11 s? What type of wave is this? Radio wave v=fƛ 3 x 108 m/s=(5 x 108 Hz)ƛ ƛ=0.6 m v=d/t 3 x 108 m/s=d/11s d=3.3 x 109 m