Light - 1 - UPSC Sci & Tech Free MCQ Test with solutions

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 laws of reflection, as stated in the textbook, are:
(i) The angle of incidence is equal to the angle of reflection.
(ii) The incident ray, the reflected ray, and the normal at the point of incidence all lie in the same plane.

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.

When two plane mirrors are placed parallel to each other, an infinite number of images of an object placed between them are formed. This is because the light rays reflect back and forth between the mirrors, creating multiple reflections that extend indefinitely, as observed in the activity with parallel mirrors.

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.

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

proper eye care practices, including: "Never rub your eyes. If particles of dust go into your eyes, wash your eyes with clean water. If there is no improvement, go to a doctor." Option C aligns with this recommendation.

Lateral inversion is a phenomenon observed in mirrors where the left and right sides are reversed in the image.

Periscopes are used in submarines to allow sailors to see above the water while remaining submerged.

When you peep through the hole, you will be able to see a variety of patterns in the tube. An interesting feature of a kaleidoscope is that you will never see the same pattern again. Designers of wallpapers and fabrics and artists often use kaleidoscopes to get ideas for new patterns.