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A plane mirror is simply a mirror with a flat surface; all of us use plane mirrors every day, so we've got plenty of experience with them. Images produced by plane mirrors have a number of properties, including:. Dealing with light in terms of rays is known as geometrical optics, for good reason: It's relatively straight-forward geometry, all based on similar triangles, but we should review that for a plane mirror. Consider an object placed a certain distance in front of a mirror, as shown in the diagram.
To figure out where the image of this object is located, a ray diagram can be used. In a ray diagram, rays of light are drawn from the object to the mirror, along with the rays that reflect off the mirror. The image will be found where the reflected rays intersect. Note that the reflected rays obey the law of reflection. What you notice is that the reflected rays diverge from the mirror; they must be extended back to find the place where they intersect, and that's where the image is.
Analyzing this a little further, it's easy to see that the height of the image is the same as the height of the object. Using the similar triangles ABC and EDC, it can also be seen that the distance from the object to the mirror is the same as the distance from the image to the mirror.
When we talk about the speed of light, we're usually talking about the speed of light in a vacuum, which is 3. When light travels through something else, such as glass, diamond, or plastic, it travels at a different speed. The speed of light in a given material is related to a quantity called the index of refraction, n, which is defined as the ratio of the speed of light in vacuum to the speed of light in the medium:.
When light travels from one medium to another, the speed changes, as does the wavelength. The index of refraction can also be stated in terms of wavelength:.
Although the speed changes and wavelength changes, the frequency of the light will be constant. The frequency, wavelength, and speed are related by:. The change in speed that occurs when light passes from one medium to another is responsible for the bending of light, or refraction, that takes place at an interface.
If light is travelling from medium 1 into medium 2, and angles are measured from the normal to the interface, the angle of transmission of the light into the second medium is related to the angle of incidence by Snell's law:. A rainbow is an arc of concentric colored bands that develops when sunlight interacts with rain drops. A rainbow occurs when rain is falling in one portion of the sky and the sun is shining in another.
For a rainbow to be seen, the sun must be behind an observer who is facing falling rain. Sunlight is refracted as it enters a raindrop, which causes the different wavelengths colors of visible light to separate. Longer wavelengths of light red are bent the least while shorter wavelengths violet are bent the most. If the angle between the refracted light and the normal to the drop surface is greater than a critical angle, the light reflects off the back of the drop.
The critical angle for water which would apply to raindrops is 48 degrees relative to the normal. Therefore, if light strikes the back of a raindrop at an angle greater than 48 degrees, it will be reflected back.
If the angle is smaller than 48 degrees, the light will simply pass on through. You can make this really simple and just hold a CD up to some sunlight — or shine a flashlight on one in a darkened room — and you will see a rainbow on the CD. The reason why a rainbow appears is because there are tiny ridges in the surface of the CD that are reflecting the light in different directions. We plan on waiting for a warm spring day to try these out!
For even more ideas and tips — check out this Rainbow Making WikiHow.
Hope you found some fun rainbow learning activities for your kids today. We certainly learned a lot and had a few very colourful days at home with these activities! Thanks for these great ideas. Do you a rainbow could be produced using a light table as the light source? The stronger the light, and the more directional and concentrated, the better.
Natural sunlight works the best! I'm a behaviour therapist, turned elementary school teacher, turned mom of one amazing son, referred to as "Onetime" in this blog.
Rainbows. , 8 OCT RainbowsNASA photographer captures a STUNNING image of rare 'hall of rainbows' · The phenomenon appeared after. Shine the light into the water where the mirror is under water (or, using the sunlight, bring This demo and the rainbows that appear in the sky share the same.
I'm so happy to have you join me in this adventure of creating, observing, and celebrating life and parenthood! Tedco Light Crystal Prism — 2. You should see a mini-rainbow appear below the glass! Making Rainbows with a CD You can make this really simple and just hold a CD up to some sunlight — or shine a flashlight on one in a darkened room — and you will see a rainbow on the CD.
Or go a little further, and try to catch the reflection of the light on some paper! More Rainbow Related Activities! Make Milky Rainbows with ingredients from your kitchen. Try making our St.
I gave up in frustration. Do you a rainbow could be produced using a light table as the light source? The reflection on the rippled surface would be nearly impossible to fake. Click here to share your story. Plane mirrors A plane mirror is simply a mirror with a flat surface; all of us use plane mirrors every day, so we've got plenty of experience with them. The light should shine through the top of the glass and directly hit the surface of the water. Featured Articles Light Experiments In other languages:
Please visit my fabulous co-hosts: Comments Thanks for these great ideas.