13. Describe how a fluorescent light bulb produces light. 14. What three things can happen when light strikes an object? 15. Using labelled diagrams. show the difference between transparent, translucent and opaque objects. 16. A basketball does not give off light.Explain how you are able to see a basketball. 17. Classify each of the following types of light according to its source: a) Firefly b) lightning c) glowstick 18. List the seven colours (in order) that make up the visible portion of the electromagnetic spectrum. 19. List 5 devices that you encounter that make use of electromagnetic waves. 20. List the properties of light, and provide a brief description of each.

13. A fluorescent light bulb produces light through a process involving fluorescence. Inside the bulb is a low-pressure mercury vapor and an inert gas. When electricity is applied, it excites the mercury atoms, causing them to emit ultraviolet (UV) light. This UV light is invisible to the human eye. The inside of the bulb is coated with a phosphor powder. When the UV light strikes the phosphor, it absorbs the UV light and re-emits it as visible light.<br /><br />14. When light strikes an object, three things can happen:<br /><br />* **Absorption:** The object can absorb some or all of the light. This absorbed light energy is usually transformed into heat. Darker objects absorb more light.<br />* **Reflection:** The object can reflect some or all of the light, bouncing it back. Mirrors are highly reflective.<br />* **Transmission:** The object can transmit some or all of the light, allowing it to pass through. Clear glass is highly transmissive.<br /><br />15.<br /><br />**Transparent:**<br /><br />[Diagram: Light rays passing straight through a rectangular object with no scattering. Label the object "Transparent" and the rays "Light".]<br /><br />**Translucent:**<br /><br />[Diagram: Light rays passing through a rectangular object, but scattering in different directions. Label the object "Translucent" and the rays "Light".]<br /><br />**Opaque:**<br /><br />[Diagram: Light rays hitting a rectangular object and being absorbed or reflected. No light passes through. Label the object "Opaque" and the rays "Light".]<br /><br /><br />16. You are able to see a basketball because it reflects light. The basketball itself does not produce light. Light from a source, such as the sun or a lamp, strikes the surface of the basketball and is reflected in various directions. Some of this reflected light enters your eyes, allowing you to see the basketball.<br /><br />17. Light sources classified:<br /><br />* a) Firefly: **Bioluminescence** (light produced by a living organism)<br />* b) Lightning: **Electrical Discharge** (light produced by the rapid movement of electrons)<br />* c) Glowstick: **Chemiluminescence** (light produced by a chemical reaction)<br /><br />18. The seven colors of the visible spectrum in order are: Red, Orange, Yellow, Green, Blue, Indigo, Violet (Remember the acronym ROY G BIV).<br /><br />19. Five devices that use electromagnetic waves:<br /><br />* Radio<br />* Microwave oven<br />* X-ray machine<br />* Cell phone<br />* Remote control<br /><br />20. Properties of light:<br /><br />* **Intensity:** The amount of energy the light wave carries. Brighter light has higher intensity.<br />* **Wavelength:** The distance between two consecutive peaks (or troughs) of a light wave. Different wavelengths correspond to different colors.<br />* **Frequency:** The number of wave peaks that pass a given point per second. Related to wavelength and energy.<br />* **Speed:** Light travels at a constant speed in a vacuum (approximately 299,792,458 meters per second).<br />* **Reflection:** The bouncing back of light when it strikes a surface.<br />* **Refraction:** The bending of light as it passes from one medium to another (e.g., from air to water).<br />* **Diffraction:** The spreading out of light waves as they pass through an opening or around an obstacle.<br /><br /><br />