Choose the correct answer:
1
2
3
4
5
6
The phenomenon by which the incident light falling on a surface is sent
back into the same medium is known as ……….
a) Reflecting
c) absorption
b) Refracting
d) None of above
The image formed by a plane mirror is always……………………
a) virtual and inverted
c) real and inverted
b) virtual and upright
d) real and upright
The relation between the focal length and radius of curvature of a mirror
is………….
a) R + 2 = f
c) R = f / 2
b) 2R =f
d) f = R / 2
An image formed by a convex mirror is always…………………
a) virtual , upright and small in size
b) real , upright and small in size
c) virtual , inverted and big in size
d) real , inverted and big in size
If the image formed by a concave mirror is virtual, upright and big in size ,
then the object is placed.
a) at the center of curvature
b) at the focus
c) in front of focus
d) between center of curvature and focus
A ray of light is incident on a plane mirror and the angle of incidence is 25o.
What is the angle of reflection?
a) 30 0
c) 25 0
b) 40 0
d) 35 0
The angle of incident = The angle of reflecting = 25o
7
8
9
The focal length of a concave mirror is 15 cm. The radius of
curvature………………….
a) 40 cm
c) 15 cm
b) 7.5 cm
d) 30 cm
f = R⁄2 → R = 2f = 2 × 15 = 30 cm
Which tool can be used to separate white light into different colors
a) Mirror
c) camera
b) Lens
d) prism
The index of refraction of benzene is 1.80. The critical angle for total
internal reflection, at a benzene to air
c) 34 0
c) 47 0
d) 65 0
d) 45 0
𝑛1 𝑠𝑛𝑖𝜃𝑐 = 𝑛2 sin 90
1
𝜃𝑐 = sin−1( ) = 34
1.8
10 The diagram shows the passage of a ray of light from
air into a substance X. The index of refraction of X is
………………………
a) 1.5
b) 1.88
c) 3
d) 2.4
𝑛1 sin 𝜃1 = 𝑛𝑥 𝑠𝑖𝑛𝜃𝑥
1 sin 40 = 𝑛𝑥 𝑠𝑖𝑛20
𝑠𝑖𝑛40
𝑛𝑥 =
= 1.88
𝑠𝑖𝑛20
11 Total internal reflection occurs when……………………
a) light passes from low refracted index to a high refracted index
b) light comes into air from vacuum
c) light goes to vacuum from air
d) light passes from high refracted index to a low refracted index
12 For which of the following cases will the total internal reflection of light be
possible?
a) Angle of incidence is less than the critical angle.
b) Angle of incidence is equal to the critical angle.
c) Angle of incidence is greater than the critical angle.
d) Angle of incidence is equal to the angle of refraction.
13 A ray of light parallel to the optic axis of a concave mirror is reflected back
a) Through the center of curvature.
b) Through the focus
c) Parallel to the optic axis.
d) Non of above
14 Light travels from air into an optical fiber with an index of refraction of
1.44. (a) If the angle of incidence is 22o, what is the angle of refraction
inside the fiber?
a) 12 0
c) 15 0
b) 36 0
d) 40 0
𝑛1 sin 𝜃1 = 𝑛2 sin 𝜃2
(1) sin 22o = 1.44 sin θ2.
θ2 = sin-1 (0.260) = 15o.
15
Calculate the angle of refraction in the lower
medium.
a) 55.76 0
b) 30.33 0
c) 19.58 0
d) 40.2 0
𝑛1 sin 𝜃1 = 𝑛2 sin 𝜃2
(1.5) sin 450 = (2.1) sin θ2.
θ2 = sin-1 (0.505 ) = 30.33.
16 Light travels through a vacuum at a speed of 3 x 108 m/s. Determine the
speed of light in water (n = 1.333)
a) 30 × 107 𝑚/𝑠
b) 22.5 × 107 m/s
𝑛=
𝑣=
𝑐
𝑐
→𝑣=
𝑣
𝑛
c) 12.5 × 107 𝑚/𝑠
d) 20.5 × 107 𝑚/𝑠
3 x 108 m/s
= 22.5 × 107 𝑚/𝑠
1.333
17 A 20 cm tall object has a 40 cm tall virtual image. The magnification is
…………..
a) 0.5
c) 3
b) 2
d) 5
′
ℎ
40
𝑀=
=
=2
ℎ 20
18 The image shown in the figure below is…
19
a) Real and upright
b) Virtual and inverted
c) Virtual and upright.
d) Real and inverted
The figure show the type of ……………..
a) converging lens
b) concave mirror
c) diverging lens
d) convex mirror
20 An image formed with a lens , that can be projected onto a screen , is called
a ………………image.
a) Virtual
c) Objective
b) Real
d) None of above
21 if the Object at the C ( center of mirror) of Concave mirror produce (.........)
image
a) real, inverted, smaller
b) virtual, upright ,larger
c) real, inverted, same size
d) virtual, inverted, same size
22 Choose the correct statements for refraction phenomena
a) The angle of incidence equals the angle of refraction
b) It is the change in direction of light when the light passes from
one medium into another medium
c) Snell's law is a formula used to describe the relationship between
the angles of incidence and refraction indexes
d) b and c is correct
23 Choose the correct statements from the figure
a)
b)
c)
d)
The reflection of light is three dimensional
Refraction phenomena occur in same medium
The angle of incidence equals the angle of reflection
The normal is the line perpendicular to a surface
24 If an object is outside the focal point on a concave mirror, the image will be
a) virtual and inverted
c) real and inverted
b) virtual and upright
d) None of above
Put true or false and correct the false and correct the false :
1) The angle of incidence is equal to the angle of reflection ( T)
2) For all plane mirrors the object distance from the mirror equal the image
distance ( T)
3) Convex mirror always make real and upright image ( F ) virtual
4) The law of reflection states that the angle of reflection is bigger than the
angle of incidence. ( F ) equal to
5) The angle that is related to a refraction angle 𝜃2 = 900 is called reflection
angle (F) critical angle
6) A concave mirror has a radius of curvature of 1.6 m . The focal length is 3.2
m ( F) focal length f = R / 2 so f = 1.6 / 2 = 0.8 m
7) If an object is outside the focal point on a concave mirror, the image will be
real and inverted object ( T )
8) A real image is produced by real rays and can be projected on a screen. ( T )
9) The type of phenomena, for which geometric optics is valid, is interference
(F). refracting or reflecting
1
1
𝑜
𝑖
10) The lens formula is ( +
mirror.
1
= ) and focal length is ( f = R / 2 ). (F)
𝑓
Solved the questions:
1- What is the critical angle for light traveling from diamond into glass,
given that the refractive index of diamond is 2.4 and the refractive index
of glass is 1.5?
Light travel from
diamond → glass
𝑛1 𝑠𝑛𝑖𝜃𝑐 = 𝑛2 sin 90
𝑛2
𝜃𝐶 = sin−1
𝑛1
1.5
𝜃𝐶 = sin−1
= 38.680
2.4
2- A lens has a focal length of 15 cm. An object is located 8 cm from the
surface of the lens.
a. Calculate how far the image is from the lens.
b. Determine whether the image is real or virtual.
c. Calculate the magnification of the image. Is the image upright or
inverted?
a.
1
1 1
= +
f
o
i
1
1 1
1
1
1
= −
→ =
− = −0.0583
i
f
o
i
15 8
∴ i = −17.15 cm
b. Negative singe mean the image is virtual.
c.
(−17.15)
𝑖
𝑀= − = −
= +2.16
𝑜
8
The image is 2.16 times as large as the object, and it is upright because the
magnification is positive.
3- A convex lens has a focal length of 25.5 cm. If the image will be at 39.3
cm . What the object's distance from the lens ?
1
1 1
= +
f
o
i
1
1 1
1
1
1
= −
→ =
−
= 0.138
o
f
i
o
25.5 39.3
∴ 0 = 72.6 cm
4- A real image is magnified by 2 when the object is placed 22 cm in front
of a concave mirror. Determine:
a. the image distance.
b. the focal length of the mirror.
a/
𝑀=−
𝑖
𝑜
∴ 𝑖 = −𝑀𝑜 = −2 × 22 = −44𝑐𝑚
the image is real, so, i must be positive ∴ 𝑖 = 44𝑐𝑚
b/
1 1 1
+ =
𝑜 𝑖 𝑓
1
1
3
+
=
= 0.068
22 44 44
1
= 0.068
𝑓
∴𝑓=
1
= 14.7𝑐𝑚
0.068
5- A light bulb is placed a distance of 20 cm from a diverging lens having a
focal length of 10 cm. Determine
a. the image distance
b. the magnification
c. Is the image upright or inverted with respect to the mirror?
a/ for diverging lens f = -10 cm
1 1 1
+ =
𝑜 𝑖 𝑓
1
1 1
1
1
1
= −
→ =
−
= −0.15
i
f
o
i
−10 20
∴ i = −6.67 cm
b/
𝑀=−
𝑀=−
𝑖
𝑜
(−6.67)
= +0.33
20
c/ It is upright because the magnification is positive.
6- A concave mirror has focal length 10 cm , an object is placed 16 cm from
the mirror. Find the location of the image and describe the image ?
1 1
1
+ =
𝑜
𝑖
𝑓
1
1 1
1
1
1
= − =
−
=
𝑖
𝑓 𝑜
10 16 26.66
𝑖 = 26.66 𝑐𝑚
𝑀= −
26.66
16
= −1.66
(real)
M is negative sign so the image is inverted
|𝑀|> 1 ( M = 1.66) the image is large size
7- An object is 25 cm in front of a converging lens of focal length 13 cm.
describe the image
1 1
1
+ =
𝑜
𝑖
𝑓
1
𝑖
=
1
𝑓
−
1
𝑜
𝑖 = 27 𝑐𝑚
𝑀= −
27
25
=
1
13
−
1
25
=
1
27
(positive sign so the image is real)
= −1.08
M is negative sign so the image is inverted
, |𝑀|> 1 ( M=1.08)
so the image is large size
8- The speed of light in a piece of glass is measured to be 2.2 x 108 m / s.
a- What is the index of refraction for this glass?
b- If a beam of light traveling in air of index of refraction n1 = 1.00
makes an angle of 8o with the normal to a surface of a piece of glass
What is the angle of refraction of the beam that passes into the glass?
a/
c
3 × 108
n= =
= 1.36
v
2.2 × 108
b/
𝑛1 sin 𝜃1 = 𝑛2 sin 𝜃2
(1) sin 8o = 1.36 sin θ2
𝜃2 = sin−1 (
1 × 𝑠𝑖𝑛8
) ≈ 5.87𝑜 = 6𝑜
1.36
9- An object is placed 45 cm in front of a convex mirror whose radius of
curvature is 30 cm. Describe the image.
We have· o = +45 cm, f = R/2 = -15 cm, we find
1 1
1
+ =
𝑜
𝑖
𝑓
1
1
1
−4
=
−
=
→ 𝑖 = −11.25𝑐𝑚
𝑖 −15 45 45
𝑖
−11.25
𝑀=− =−
= +0.25
𝑜
45
Since the magnification is positive, the image is upright and, in this case, is
one-fourth the size of the object.
10- A ray of light passing through a glass prism of refracting angle 60º,
undergoes a minimum deviation of 30º. Calculate
a) Refracted index of prism
b) The velocity of light in glass if the velocity of light in air is 3×108 m /s
a/
n = sin [(ψ + φ) / 2] / sin (φ/2)
n= sin [(30 + 60º) / 2] / sin (60º/2)
n = 1.41
b/
𝑛=
𝑐
𝑐
→ 𝑣=
𝑣
𝑛
3 × 108
𝑣=
= 212.7 × 106 𝑚/𝑠
1.41