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Q1. A material that allows light to pass through it without significant distortion is known as

• 1) Opaque
• 2) Transparent
• 3) Translucent
• 4) Luminous

Solution

A material that allows light to pass through it without significant distortion is known as transparent.

Q2. ___________ reflections are used in periscopes.

Solution

Multiple reflections are used in periscopes.

Q3. We can see an object only when the light may have been

• 1) Reflected by the object
• 2) Emitted by the object
• 3) Absorbed by the object
• 4) Emitted or reflected by the object

Solution

It is only when light from an object enters our eyes that we see the object. The light may have been emitted by the object or may have been reflected by it.

Q4. Which of the following is an optical aid used by visually challenged persons to develop their capabilities?

• 1) All of the above
• 2) Telescopic aids
• 3) Magnifiers
• 4) Bifocal lenses

Solution

All the aids can be used by visually challenged persons to develop their capabilities.

Q5. What are the characteristics of Braille system?

Solution

(i) It has 63 dot patterns or characters. (ii) Each character represents a letter, a combination of letters, a common word or a grammatical sign. (iii) Dots are arranged in cells of two vertical rows of three dots each.

Q6. The crystalline lens of people at old age becomes milky and cloudy. This condition is called:

• 1) Cataract
• 2) Presbypoia
• 3) Myopia
• 4) Hypermetropia

Solution

The crystalline lens of people at old age becomes milky and cloudy. This condition is called cataract.

Q7. What is lateral inversion?

Solution

Lateral inversion is the phenomena when in an image formed by a mirror the left of the object appears on the right and the right appears on the left.

Q8. The incident ray and the reflected ray from a mirror are mutually perpendicular to each other. The angle of incidence is

• 1) 22.5^o
• 2) zero
• 3) 45^o
• 4) 90^o

Solution

Angle of incidence + Angle of reflection = 90^o Angle of incidence = Angle of reflection  2 x Angle of incidence = 90^o Angle of incidence = 45^o

Q9. A ray of light is incident on a plane mirror and the angle of reflection is 50^o. The angle incidence is

• 1) 100^o
• 2) 50^o
• 3) 25^o
• 4) 90^o

Solution

Angle of incidence = angle of reflection = 50^o

Q10. Which region in human eye is considered as blind spot?

Solution

At the junction of the optic nerve and the retina, there are no sensory cells, so no vision is possible at that spot. This region of eye is called blind spot.

Q11. Mention any three features of the image obtained by a plane mirror.

Solution

Features of the image obtained by a plane mirror are: (i) The image formed is virtual. (ii) The image formed is laterally inverted. (iii) The image formed is of the same size as the object.

Q12. Where an image is formed in human eye? Name the nerve which transmits the sensations felt by the nerve cells for an image.

Solution

An image is formed on the retina in human eye. Optic nerve transmits the sensations felt by the nerve cells for an image.

Q13. Braille was developed in 1821 by _________ Braille a visually challenged person.

Solution

Braille was developed in 1821 by Louis Braille a visually challenged person.

Q14. How the eye perceives that a still object is moving?

Solution

The impression of an object persists for about 1/16^th of a second. So, if still images of a moving object are flashed on the eye at a rate faster than 16 per second, then the eye perceives that the object is moving.

Q15. The human eye forms the image of an object at its

• 1) Iris
• 2) Pupil
• 3) Cornea
• 4) Retina

Solution

The human eye forms the image of an object at its retina.

Q16. Regular reflection takes place when a beam of light strikes

• 1) Concrete wall
• 2) Polished wooden table
• 3) Chalk powder
• 4) Cardboard surface   

Solution

Regular reflection takes place at smooth and polished surfaces.

Q17. Diffused reflection is

• 1) Caused by the irregularities in the reflecting surface
• 2) Caused when the incident rays are not parallel to each other
• 3) Due to the failure of laws of reflection
• 4) Caused when the intensity of incident rays is not high

Solution

Diffused reflection is not due to the failure of the laws of reflection. It is caused by the irregularities in the reflecting surface, like that of a cardboard.

Q18. In the diagram

• 1) AO is the incident ray, OB is the normal and OC is the reflected ray
• 2) AO is the normal, OB is the incident ray and OC is the reflected ray
• 3) AO is the reflected ray, OB is the normal and OC is the incident ray
• 4) AO is the incident ray, OB is the reflected ray and OC is the normal

Solution

AO is the incident ray, OB is the normal and OC is the reflected ray.

Q19. What causes diffused reflection?

• 1) Either A or B
• 2) Failure of laws of reflection
• 3) Both A and B
• 4) Irregularities in the reflecting surface

Solution

Irregularities in the reflecting surface cause diffused reflection.

Q20. What device is used to correct eye defects?

• 1) Microscope
• 2) Lenses
• 3) Mirror
• 4) Glass slab

Solution

Lenses are used to correct eye defects.

Q21. What is cataract? How it can be treated?

Solution

Cataract is a condition in which the eye lens becomes cloudy and the eyesight becomes foggy. It can be treated by surgery. The opaque lens is removed and a new artificial lens is inserted.

Q22. What are the vitamins and minerals which help in neutralizing the free radicals that can have a damaging effect on the retina, called?

• 1) Antioxidants
• 2) Oxidants
• 3) Radicals
• 4) Antiradicals

Solution

Antioxidants help in neutralizing the free radicals that can have a damaging effect on the retina.

Q23. What is the most interesting feature of the Kaleidoscope? What is the advantage of this feature?

Solution

The most interesting feature of the Kaleidoscope is that the same pattern of an object is not seen again. Designers of paper and fabrics and artists use Kaleidoscope to get ideas for new patterns.

Q24. State the laws of reflection.

Solution

(i) The angle of incidence is always equal to the angle of reflection. (ii) The incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane.

Q25. Why moon is considered as an illuminated object?

Solution

Moon is considered as an illuminated object because it receives the light from the sun and reflects it back. Such objects which shine in the light of other objects are called illuminated objects.

Q26. How the visually challenged persons identify things?

Solution

The visually challenged persons try to identify things by touching and listening to voices more carefully.

Q27. What are the uses of periscopes?

Solution

Periscopes are used in submarines, tanks and also by soldiers in bunkers to see things outside.

Q28. The image formed by the eye lens on the retina is

• 1) Real, upright and diminished
• 2) Virtual, inverted and diminished
• 3) Real, upright and enlarged
• 4) Real, inverted and diminished

Solution

The image formed by the eye lens on the retina is real, inverted, diminished.

Q29. What is the principal behind the working of a Kaleidoscope?

Solution

The principal behind the working of a Kaleidoscope is that a number of images are formed by mirror placed at an angle to another.

Q30. Name the two types of cells which make us see objects and write their function.

Solution

(i) Cones - These are sensitive to bright light and sense colours. (ii) Rods - These are sensitive to dim light.

Q31. What is diffused or irregular reflection?

Solution

When all the parallel rays reflected from a plane mirror are not parallel, the reflection is said to be diffused or irregular reflection.

Q32. Who invented a system of reading and writing used by people who are blind or visually impaired.

• 1) Louis Philippe
• 2) Nikola Tesla
• 3) Louis Braille
• 4) Carl Sagan

Solution

Louis Braille invented a system of reading and writing used by people who are blind or visually impaired.

Q33. How the visually challenged people learn the Braille system?

Solution

The visually challenged people learn the Braille system by beginning with letters, then special characters and letter combinations. Methods depend upon recognition by touching and each character has to be memorized.

Q34. Draw the structure of human eye and label any three parts of it.

Solution

Structure of human eye:

Q35. What are the causes of blindness?

Solution

(i) Blindness can be due to birth defects. (ii) Some persons may lose their eyesight permanently due to some disease.

Q36. What is angle of incidence and angle of reflection?

Solution

The angle between the normal and the incident ray is called the angle of incidence and the angle formed between the normal and the reflected ray is called the angle of reflection.

Q37. What is iris? Write its function.

Solution

The iris is a dark muscular structure which gives eye its distinct colours. It controls the amount of light entering into the eye.