TOPIC: LIGHT AS AN ELECTROMAGNETIC WAVE

Show the solution and drawing with the correct angle using protractor.

2. An incident ray of light strikes a smooth surface at an angle of 30 degrees relative to the reflecting surface. What would be the angle of reflection?7. A ray of light travels from air into a glass at an angle of incidence of 40degrees. If it is refracted at 30 degrees from the normal line, what is the index of refraction of light in the glass?2. A ray of light strikes a plane mirror at an angle of incidence of 35 degrees. What is the value of the angle of reflection?7. A ray of light is incident from air to water at 50 degrees. The ray will be refracted at what angle from the normal?Activity 1. Let's Draw it! Directions. Draw where the rays will be reflected back from the surface of the mirror and identify the values of the reflected angles if supposedly several rays of light strike a mirror at different angle. Write your answer on a sheet of paper. incident ray 1 incident ray 2 incident ray 3 normal line 110 30 45 mirror 1. angle of reflection = 2. Angle of reflection = 3. Angle of reflection = Activity 2. From Top to Bottom! Directions. On a sheet of paper, arrange the following materials below according to the speed of light as it travels through the medium by writing 5 for the fastest and 1 for the slowest. ethyl alcohol Plexiglas diamond zircon iceActivity 3. "Light me Pass Through!" Directions. On a sheet of paper, draw how each ray gets refracted by completing the illustrations below. a. b. air normal glass normal water air c. air normal d. air normal water diamondElectromagnetic waves Electromagnetic radiation is a form of energy emitted by moving charged particles. As it travels through space, it behaves like a wave and has an oscillating electric field component and an oscillating magnetic field. These waves oscillate perpendicular to and in phase with one another. (Lumen, Boundless Physics) Wavelength and frequency are properties that may be used to describe electromagnetic wave. Wavelength is the distance from one crest to the next which can be measured in meters. Frequency is the number of waves that passes by a given point each second. These two properties are inversely proportional to each other and may vary for every type of EM radiation. The speed of electromagnetic waves in a vacuum remains constant at 3.0 x 105 m/sec, the speed of light. The wavelength or frequency of EM wave can be calculated using the equation below: c=Af=Af where: c = the constant 3.0 x 10# m/sec (the speed of light in a vacuum) A = wavelength in meters (m) and f = frequency in hertz (1/s) Light as Electromagnetic Wave Visible light is an electromagnetic radiation with a wavelength range from 400 - 700 nanometers. Among the different EM radiations only light can be detected by the human eye. Optics is the branch of physics that studies the behavior and properties of light including its interactions with matter and the construction of instruments that use or detect it. Light travels in a vacuum at a constant speed of 299 792 458 meters per second. However, for ordinary purposes, this value is rounded off to 300 000 000 m/s.Reflection of Light One interesting property of light just like other types of EM waves is reflection. Reflection is the turning back of light ray when it hits a medium. incident ray reflected ray Source: http://farside.ph.utexas.edu/teaching/3021/lecturesode127.html In the diagram, a ray from the light source is also known as the incident ray. The reflected ray is reflected after striking the mirror. Normal line is the line drawn perpendicular to the surface of the mirror. The normal line divides the angle between the incident ray and the reflected ray into two equal angles. The angle between the incident ray and the normal line is known as the angle of incidence. The angle between the reflected ray and the normal line is known as the angle of reflection. The law of reflection states that when a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection. Types of Reflection Regular Reflection Diffuse Reflection incident rays Reflected Rays Incident rays enected Pays Eg. plane mirror or any other surface This is like any surface that we can that produces a reflected image. see but does not reflect an image Source: http://www.rebeccapaton.net/ rainbows/rfictn.htm The two types of the reflection of light are the regular or specular reflection and the irregular or diffuse reflection. Regular or specular reflection occurs when light strikes a smooth and well-polished surface such as a mirror. When parallel rays of light strike a smooth flat surface, the rays are reflected parallel to each other, hence there is an image formed. While a diffuse reflection occurs when light hits a rough surface like blackboard, trees, wall, etc. Rays of light are reflected in different directions. There is no image formation in this type of reflection. However, diffuse reflection is very important because it enables us to see things even in shaded areas. Refraction Refraction is bending of the path of a light when it passes from one medium to another of different optical density. Light refracts because its speed changes (whether slows down or speeds up) upon crossing the boundary of two media. The cause of the change in speed of light is the optical density of a material.The optical density of a material relates to the sluggish tendency of the atoms of a material to maintain the absorbed energy of an electromagnetic wave in the form of vibrating electrons before reemitting it as a new electromagnetic disturbance (Topper Learning). The more optically denser a material is, the slower the light will travel into it, so light travels faster in an optically less dense medium. Index of refraction is the measure of the bending of a ray of light when passing from one medium into another (microscopyu.com). It is also equal to the ratio of the speed of light c in a vacuum to the second medium of greater density v, or: n = c/v. The table below lists index of refraction values for a variety of media. The materials listed on the upper part are those materials which light travels fastest; these are the least optically dense materials. The materials listed on the lower part are those materials which light travels slowest; these are the most optically dense materials. So as the index of refraction value increases, the optical density increases, and the speed of light in that material decreases. (physicsclassroom.com) Material Index of Refraction vacuum 1.0000