Light

Question 1

What is reflection?

Answer 1

Bouncing back of light in the same medium

Question 2

What is the law of reflection

Answer 2

The incident ray reflected ray and normal all lies on the same plane.
Angle of incidence= angle of reflection

Question 3

What are the types of spherical mirrors?

Answer 3

Concave mirror - caved part is reflective. Converging
Convex mirror - bulging out reflecting mirror. Diverging

Question 4

What are the types of image ?

Answer 4

Real and inverted image - can be obtained on screen. Formed when light rays actually meet
Virtual and erect image - cannot be obtained on the screen. formed when light rays appear to meet

Question 5

What is the centre of curvature and radius of curvature

Answer 5

It is the centre of the mirror denoted by C.
Radius of curvature is the distance between the centre of curvature and pole denoted by R.

Question 6

Where is focus and focal length ??

Answer 6

It lies between the centre of curvature and pole denoted by F.
Focal length is the distance between focus and pole denoted by f.

Question 7

What is pole ?

Answer 7

It is the centre of the mirror surface

Question 8

What is the principal axis?

Answer 8

An imaginary line passing through C F and P.

Question 9

What is the relationship between f and R

Answer 9

f=R/2

Question 10

When the incident ray is parallel to the principal axis it passes through …….

Answer 10

Focus (F)

Question 11

When the rays of light come from infinity they are ………..

Answer 11

Parallel

Question 12

If a ray of light passes through focus after reflection then it is ………..

Answer 12

Parallel to principal axis

Question 13

If the incident ray passes through Centre of curvature it ………..

Answer 13

Bounces back at the same path forming 0°

Question 14

When the reflected ray passes through the pole it reflects ………

Answer 14

Obliquely angle of incidence= angle of reflection both made by principal axis

Question 15

Concave mirror
When an object is at infinity ♾️

Answer 15

The image formed is highly diminished real and inverted and is formed at focus.

Question 16

Concave mirror
When an object is kept beyond C

Answer 16

The image formed is real and inverted between C and F and smaller / diminished.

Question 17

Concave mirror
When an object is kept at C

Answer 17

The image formed is real and inverted at C and is of the same size.

Question 18

Concave mirror
When an object is placed between C and F

Answer 18

The image formed is beyond C larger and real and inverted.

Question 19

Concave mirror
When an object is kept at F

Answer 19

The image formed would be at infinity and real and inverted larger.

Question 20

Concave mirror
When the object is between F and P

Answer 20

The image formed is behind the mirror virtual and erect and enlarged

Question 21

What are the uses of concave mirrors?

Answer 21

Used in shaving mirror headlight solar furnace and also by dentists.
Dentists need an enlarged, virtual image as the object is kept near the mirror the image formed is enlarged and erect.
In the solar furnace and headlight a strong parallel beam of light is required.

Question 22

Convex mirror
When an object is at infinity

Answer 22

Image is formed at focus virtual and erect and highly diminished

Question 23

Convex mirror
When the object is between infinity and Pole.

Answer 23

The image is formed between P and F virtual and erect smaller or diminished.

Question 24

What are the uses of a convex mirror?

Answer 24

Used where a wide field of view is required like parking mirrors and rear view mirrors.

Question 25

Sign convention of spherical mirrors

Answer 25

Left of the mirror -ve Right of the mirror+ve Above principal axis+ve Below principal axis -ve

Question 26

What is the mirror formula?

Answer 26

1/v + 1/u = 1/f u- obj distance v - image distance f - focal length

Question 27

What is magnification?

Answer 27

It is the extent to which the image size has increased or decreased.

Question 28

What is the formula of magnification?

Answer 28

m = hi/ho = -v/u

Question 29

If magnification is positive then the image is .............

Answer 29

Virtual

Question 30

If magnification is -ve image is ...................

Answer 30

Real

Question 31

If m is 1 then the image is ................

Answer 31

Same size as the object

Question 32

If m > 1 then the image is ...................

Answer 32

Enlarged

Question 33

If m < 1 then image is

Answer 33

Diminished

Question 34

The object distance is always ...............

Answer 34

-ve

Question 35

The focal length of the concave mirror is

Answer 35

-ve

Question 36

The focal length of the convex mirror is

Answer 36

+ve

Question 37

What is a refraction?

Answer 37

When light travels from one medium to another it changes its direction and bends and this bending of light is called refraction

Question 38

What is optical rearer or denser medium ?

Answer 38

Optical rearer medium has high speed of light and is less dense Optical denser medium has less speed of light as it is more denser

Question 39

What are the reasons for refraction?

Answer 39

-Speed changes due to optical density. - Change in direction and medium

Question 40

If light travels from rearer to denser it .........

Answer 40

Bends towards normal

Question 41

If light travels from denser to rarer ...........

Answer 41

Bends away from normal

Question 42

What are the laws of refraction?

Answer 42

I) The incident ray normal the refracted ray all lie on the same plane (plane not medium) II) Snell law - if the medium is same the sine of angle of incidence upon sine of angle of refraction is constant.

Question 43

What is refractive index?

Answer 43

It is inversely proportioned to speed of light. Denoted by n or u

Question 44

What is the refracted index of medium a with respect to medium b

Answer 44

Speed of light in medium b / speed of light in medium a OR Refractive index of medium a / refraction index of medium b

Question 45

Speed of light in vacuum

Answer 45

3×10 with the power of 8 m/s

Question 46

What is concave and convex lens ?

Answer 46

Concave lens diverges the light rays Convex lens converages the light rays

Question 47

What are the parts of the lens ?

Answer 47

2 focus 2 centre of curvature and one optical centre - O

Question 48

Parallel rays in a lens pass through

Answer 48

Focus

Question 49

Focal length of concave lens

Answer 49

-ve

Question 50

Focal length of covex mirror

Answer 50

+ve

Question 51

Light ray passing through focus refracts

Answer 51

Parallel to principal axis

Question 52

Light rays passing through optical centre

Answer 52

Stays the same

Question 53

**CONVEX LENS** Object is at infinity then image at

Answer 53

Focus

Question 54

**CONVEX LENS** Object is beyond C image at

Answer 54

BETWEEN C AND F

Question 55

**CONVEX LENS** When objects at C images at

Answer 55

C

Question 56

**CONVEX LENS** When obj is between C and F image is

Answer 56

Beyond C

Question 57

**CONVEX LENS** When objects at F image at

Answer 57

Infinity

Question 58

**CONVEX LENS** Object between F and P image

Answer 58

Virtual and erect

Question 59

**CONCAVE LENS** When object at infinity

Answer 59

Image at focus

Question 60

**CONCAVE LENS** Object at finite distance

Answer 60

Image between focus And O

Question 61

What is lens formulae ?

Answer 61

1/v-1/u=1/f

Question 62

What is the magnification of the lens?

Answer 62

m=hi/ho =-v/u

Question 63

What is power ?

Answer 63

It is the reciprocal of focal length denoted by D Dipotre formula - 1/f when f in m and 100/f when f in cm

Question 64

What is the total power upon combining two lens

Answer 64

P1+P2

Question 65

What is the power of plane mirror

Answer 65

0

Question 66

What is the focal length of plane mirror

Answer 66

♾️

Question 67

What is absolute refractive index?

Answer 67

Refractive index with the respect to air