Table of contents | |
Light Travels Along a Straight line | |
Reflection of Light | |
Playing With Spherical Mirrors | |
Images Formed by Lens | |
Sunlight - White or Colored? |
Have you noticed sunlight shining into a room through a small hole, or the bright lights from a car at night? These beams of light help us see and show how light travels. Let's learn more about how light works and why it’s important!
Light is a form of energy that allows us to see the world around us. It travels in straight lines and can move through different mediums like air, water, and glass.
This characteristic of light can be explained by a Candle and Pipe Experiment.
Conclusion: So, when light's path is blocked or bent, you won't be able to see the light source, just like with the candle and the bent pipe.
When light hits a shiny surface like a stainless-steel plate, steel spoon, or even the surface of water, it can change direction. This is known as reflection.
Reflection of light from a mirror
Erect: An image is said to be erect if the image is formed the same side up as that of the object.
Inverted: The image will be called Inverted if it is formed upside down compared to the object.
Inverted image of a candle
This happens because the mirror switches left and right sides. So, what looks like left in the mirror is actually right, and what looks like right is actually left.Left- Right Inversion
Interesting Fact: Why is the word ‘AMBULANCE’ painted on an ambulance left-right inverted?
The left-right reversal of images in a mirror causes the word "ambulance" to be easily readable for the driver of a vehicle ahead when seen in the rearview mirror.
left-right reversal of images
Spherical mirrors are mirrors that have a curved surface, like a part of a sphere (a round object like a ball).
Types of Spherical Mirrors:
Concave Mirror:
Convex Mirror:
Where You See Them:
Types of Mirrors
There are two types of images formed
1. Real Image: Images that can be captured on a screen are known as real images. For example, in a camera, images are real and can be captured on the negative, which acts as a screen.
2. Virtual Image: The image formed by a plane mirror cannot be captured on a screen and is called a virtual image.
Real and Virtual Image
A lens is a piece of transparent material, usually glass or plastic, that bends light to help us see things more clearly. Lenses are used in many everyday objects like spectacles (glasses), telescopes (to see faraway things), and microscopes (to see very tiny things).
Depending upon its shape a lens can be categorized as:
1. Convex Lens - A Convex Lens is curved outwards. It is thicker in the center and narrows down at the edges. It merges the light rays passing through it at a certain point. Therefore, it is also called a Converging Lens.
2. Concave Lens - A Concave Lens is curved inwards. It has wider edges and a thinner center. It reflects back the light that travels through it in different directions. Therefore, it is also called a Diverging Lens.
Lens
Converging and Diverging Lens
Applications of Lenses
Lenses are used in magnifying glasses, peep holes, cameras, bioscopes, binoculars, telescopes, microscopes and projectors. A refracting telescope uses a concave mirror and a convex lens.
Image by a convex lens for object placed at different distance from it
Virtual image by convex lens Image by a concave lens
A band of colors extending from violet to red is a rainbow. A rainbow is formed by the reflection of the sun's rays through raindrops.
A rainbow is a natural event where sunlight is reflected by water droplets in the air. It forms an arc in the sky and showcases seven distinct colors: red, orange, yellow, green, blue, indigo, and violet.
This occurrence shows that sunlight is actually composed of seven different colored lights, which become visible through reflection.
Just like how the soap bubbles and CDs show different colors when light hits them, sunlight is made up of many colors that can be separated and seen. This is why we can create rainbows or see colorful reflections!
Note: If you divide a disk into 7 parts and paint each part with a different color of the rainbow, when you spin the disk really fast in bright light, the colors all blend together, and the disk looks white.
Let's understand this with interesting activity through a Prism:
A prism splits a beam of sunlight into seven colors
Newton's Disc
When you divide a disk into seven sections and paint each with a different color of the rainbow, you get what's known as Newton's disc. When you spin the disc quickly in daylight, the colors blend together, giving the appearance of a whitish color.
Newton's Disc
111 videos|246 docs|28 tests
|
1. What is the principle behind light traveling along a straight line? |
2. How does reflection of light occur? |
3. How do spherical mirrors affect the reflection of light? |
4. What are the different types of images formed by lenses? |
5. Is sunlight white or colored? |
|
Explore Courses for Class 7 exam
|