Say TRUE or False.We are able to see things around us with the help of regular reflection

A person can see clearly objects only when they lie between 50 cm and 400 cm from his eyes.In order to increase the maximum distance of distinct vision to infinity,the type and power of the correcting lens,the person has to use , will be

Answer the following questions: a. In a single slit diffraction experiment, the width of the slit is made double the original width. How does this affect the size and intensity of the cenral diffraction band? b. In what way is diffraction from each slit related to the interference pattern in a double slit experiment? c. When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the shadow of the obstacle. Explain why. d. Two students are separated by a 7m partition wall in a room 10 m high. If both light and sound waves can bend around obstacles, howare the students unable to see each other even though they can converse easily. e.Ray optics is based on the assumption that the light travels in a straight lin. Diffraction effects (observed when light propagates through small apertures/slits a or around small obstacles) disprove this assumption. Yet the ray options assumptioni is so commonly used in understanding location and several other properties of images in optical instruments. What is the justification?

Assertion and Reason. Mark the correct choice as:Assertion:We can see the rainbow in the sky when the rain starts falling after a spell of bright sunlight. Reason: The rainbow is formed due to disprsion of light.

A man whose eye-level is 2 m above the ground wishes to find the height of a tree. He places a mirror horizontally on the ground 20 m from the tree and finds that if he stands at a point C which is 4 m from the mirror B, he can see the reflection of the top of the tree. How height is the tree?

A man whose eye-level is 2 m above the ground wishes to find the height of a tree. He places a mirror horizontally on the ground 20 m from the tree and finds that if he stands at a point C which is 4m from the mirror B, he can see the reflection of the top of the tree. How height is the tree ?

If we put a cardboard (say 20 cm xx 20 cm) between a light source and our eyes, we can't see the light. But when we put the same cardboard between a sound source and our ear, we hear the sound almost clearly, Explain.

The yellow colour has a greater luminous efficiency as compared to the other colours. Can we increase the illuminating power of a white light source by putting a yellow plastic paper around this source ?

Reaction time : When a situation demands our immediate action, it takes some time before we really respond. Reaction time is the time a person takes to observe, think and act. For example, if a person is driving and suddenly a boy appears on the road, then the time elapsed before he slams the brakes of the car is the reaction time. Reaction time depends on complexity of the situation and on an individual. You can measure your reaction time by a simple experiment. Take a ruler and ask your friend to drop it vertically through the gap between your thumb and forefinger (Fig.). After you catch it, find the distance d travelled by the ruler. In a particular case, d was found to be 21.0 cm. Estimate reaction time.