Test: Light - 1 - Class 8 MCQ

The Braille system is a tactile writing system used by people who are visually impaired. It consists of patterns of raised dots arranged within a six-dot cell. Each cell can have any combination of raised or flat dots, resulting in a total of 63 possible combinations (not including the space with no dots raised). These combinations are used to represent letters, numbers, punctuation marks, and even whole words or symbols.

Here's how the 63 combinations are calculated:

• A Braille cell has 6 positions for dots.
• Each dot in a position can either be raised or flat, which gives 2 choices per dot.
• The total number of combinations is calculated as 26−1=64−1=632^6 - 1 = 64 - 1 = 6326−1=64−1=63 (subtracting one because the configuration with no dots raised is not counted as a character).

This is why the Braille system can represent a wide range of characters with 63 patterns.

The object through which light can pass easily is called transparent object. Glass, water and thin plastic sheets are transparent object.

The band of seven colours obtained on screen when white colour of light possesses through a prism on screen after dispersion is called spectrum.

- True
- Explanation:
- The statement is known as the law of reflection.
- According to this law, the angle of incidence is always equal to the angle of reflection.
- This principle holds true for light or any other wave reflecting off a surface.
- It is a fundamental concept in optics and is crucial in understanding how light behaves when it interacts with surfaces.

Iris

Iris regulates the amount of light entering the eye by adjusting its size. Iris is a thin membrane, which controls pupil which in turn regulates the amount of light entering the eye.

The objects that emit light is called luminous object. Sun, stars, bulb, tube etc are example of luminous object.

The iris in our eyes acts like a camera lens, adjusting the size of the pupil to control how much light comes in.
This helps us see clearly in different light conditions. 

When light strikes a surface and bounces back, we call it the reflected ray. It's like when you throw a ball against a wall and it bounces back to you. The reflected ray is what we see when light hits a mirror or any shiny surface and comes back to our eyes.

In human eyes, image is formed on retina. Retina forms the backward parts of eye ball having rods and cones to form image.

Speed of light is fastest in air. Speed of light decreases with increase in density. Light travels slowest in diamond.

Louis Braille invented the Braille System to help visually challenged people. This system uses patterns of raised dots that people can touch to read words with their fingers. It's like feeling a secret code with your hands to understand words better.

Convex lens forms a real, point sized image at focus, the object is placed at infinity.

Splitting of white rays of light into seven colour when passes through a prism is called dispersion of light.

• When two plane mirrors are set at right angles to each other, multiple images of an object can be formed.
• This happens because the light reflects off one mirror and then reflects off the other mirror, creating different images due to the angles at which the mirrors are placed.