Light! 7SCIENCE

Characteristics of Light Light carries energy – Electromagnetic wave – Sources of light give off light waves A narrow beam of light travelling in a straight line is called a light ray A source of light gives off light rays in all directions

Light and Matter You can see things because light is bouncing off an object and into your eyes – This is called reflection When light rays hit an object, the light can: – Be absorbed – Be reflected – Pass through the object

Electromagnetic Spectrum Remember that all waves have a wavelength and a frequency, which depends on the wavelength – As wavelength decreases, frequency increases Electromagnetic waves we see as light are part of the electromagnetic spectrum – Electromagnetic waves are organized by their wavelengths Radio waves carry the least energy while gamma rays (used to treat cancer) have the most energy

Electromagnetic spectrum: Visible light Visible light is the small range in the electromagnetic spectrum that we can see Different colors are electromagnetic waves of different wavelengths – Which color has the longest wavelength? Shortest? When light hits an object, the color we see is the specific wavelength reflected in an object – Ex: objects that look red are reflecting red waves and absorbing the other waves – Ex: objects that look white reflect all the colors while a object that is black absorbs all the colors

Color and Light Color is a mixture of light waves Any color can be made by mixing different wavelengths of red, green and blue light – Primary light colors Materials used to change the color of other objects is called a pigment – Primary pigment colors are: magenta, yellow and cyan

Complete from text: pg. 72 Section Assessment You DO NOT have to write out the question. Please write out your answers in full sentences to questions 1,3,4 and 5 and hand in for the end of class 1.Which has a higher frequency, red or blue light? 3. What colors are reflected by an object that appears black? 4. Why is it cooler to wear light-colored clothing on a hot day than dark clothes? 5. A white plastic bowl and a black plastic bowl are sitting in the sunlight. You observe that the black bowl feels warmer than the white bowl. From this information, explain which bowl absorbs and which bowl reflects more light.