Question 1

An oil layer that is 5.0 cm thick is spread smoothly and evenly over the surface of water on a windless day.A light ray from the air above enters the oil at 45° with the normal and then goes into the water.What is the angle of refraction of this ray in the water? The index of refraction for the oil is 1.15,and for water it is 1.33.

Accepted Answer

A) 27° 
B) 32° 
C) 36° 
D) 39°

Question 2

A cup that is 6.0 cm tall is in front of a concave lens.The image of the cup is 2.5 cm tall and 7.5 cm from the lens.What is the focal length of the lens?

Accepted Answer

A) -6.0 cm 
B) -7.5 cm 
C) -13 cm 
D) +18 cm 
E) +6.0 cm

Question 3

Starting from very far away,an object is moved closer and closer to a converging lens,eventually reaching the lens.What happens to its image formed by that lens? (There could be more than one correct choice. )

Accepted Answer

A) The image gets closer and closer to the lens. 
B) The image gets farther and farther from the lens. 
C) The image eventually changes from virtual to real. 
D) The image eventually changes from real to virtual. 
E) The image keeps getting larger and larger.

Question 4

A negative magnification for a mirror means that

Accepted Answer

A) the image is inverted,and the mirror could be either concave or convex. 
B) the image is upright,and the mirror is convex. 
C) the image is inverted,and the mirror is convex. 
D) the image is inverted,and the mirror is concave. 
E) the image is upright,and the mirror could be either concave or convex.

Question 5

The index of refraction of a certain glass is measured to be 1.5.What is the speed of light in that glass? (c = 3.0 × 108 m/s)

Accepted Answer

A) 1.0 × 108 m/s 
B) 2.0 × 108 m/s 
C) 3.0 × 108 m/s 
D) 4.0 × 108 m/s 
E) 5.0 × 108 m/s

Question 6

The image formed in a plane mirror is

Accepted Answer

A) at the same distance in front of the mirror as the object is in front of the mirror. 
B) a real image behind the mirror. 
C) at the same distance behind the mirror as the object is in front of the mirror. 
D) at a shorter distance behind the mirror than the distance the object is in front of the mirror. 
E) at a larger distance behind the mirror than the distance the object is in front of the mirror.

Question 7

A glass plate having an index of refraction is 1.66 is immersed in a certain alcohol.The surface of the glass is inclined at an angle of 44° with the vertical.When a horizontal ray in the glass strikes the interface,you observe that it is at the critical angle.What is the index of refraction of the alcohol?

Accepted Answer

A) 1.15 
B) 1.13 
C) 1.11 
D) 1.09 
E) 1.17

Question 8

An object is placed on the left side of a thin lens,and the image of this object is formed on the left side of the lens.Which of the following statements must be true? (There could be more than one correct choice. )

Accepted Answer

A) The lens must be a diverging lens,and the image is upright. 
B) The lens must be a converging lens,and the image is upright. 
C) The image is upright and virtual. 
D) The lens could be either a converging or a diverging lens,and the image is upright. 
E) The image is inverted and real.

Question 9

A tank holds a layer of oil,of thickness To = 1.65 m,that floats on a layer of syrup of thickness Ts = 0.830 m,as shown in the figure.Both liquids are clear and do not mix together.A light ray,originating at the bottom of the tank at point P,crosses the oil-syrup interface at a point 0.900 m from the axis.The ray continues and arrives at the oil-air interface,2.00 m to the right of P and at the critical angle.What is the index of refraction of the syrup?

Accepted Answer

A) 1.36 
B) 1.25 
C) 1.94 
D) 1.75 
E) 1.54

Question 10

A beam of light traveling in air strikes a glass slab at an angle of incidence less than 90°.After entering the glass slab,what does the beam of light do? (There could be more than one correct choice. )

Accepted Answer

A) I follows the same path as before it struck the glass. 
B) It follows the normal to the glass slab. 
C) It bends away from the normal at the point of contact. 
D) It bends closer to the normal at the point of contact. 
E) It slows down.

Question 11

A thin flashlight beam traveling in air strikes a glass plate at an angle of 52° with the plane of the surface of the plate.If the index of refraction of the glass is 1.4,what angle will the beam make with the normal in the glass?

Accepted Answer

A) 34° 
B) 64° 
C) 26° 
D) 56° 
E) 38°

Question 12

An object is 5.7 cm from a spherical concave mirror.If the image is 4.7 cm tall and 10 cm from the mirror,how tall is the object?

Accepted Answer

A) 12 cm 
B) 11 cm 
C) 8.2 cm 
D) 2.7 cm

Question 13

A convex spherical mirror has a focal length of magnitude 20 cm.If an object is placed 10 cm in front of the mirror on the mirror's axis,where is the image located?

Accepted Answer

A) 20 cm behind the mirror 
B) 20 cm in front of the mirror 
C) 6.7 cm behind the mirror 
D) 6.7 cm in front of the mirror

Question 14

A cell phone that is 8.90 cm tall is placed in front of a convex mirror.The image of the phone is 7.80 cm tall and is located 14.8 cm from a mirror.What is the mirror's focal length?

Accepted Answer

A) -120 cm 
B) -105 cm 
C) +16.9 cm 
D) -13.0 cm 
E) +120 cm

Question 15

A coin is 12 cm in front of a converging lens with focal length of magnitude 4.0 cm.Where is the image?

Accepted Answer

A) 8.0 cm behind the lens 
B) 6.0 cm in front of the lens 
C) 6.0 cm behind the lens 
D) 4.0 cm in front of the lens

Question 16

An object is placed 21 cm from a concave lens having a focal length of magnitude 25 cm.What is the magnification?

Accepted Answer

A) -0.54 
B) 0.54 
C) -0.32 
D) -0.22 
E) 0.22

Question 17

A lab specimen is 15.2 mm from a converging lens.The image is 4.0 mm tall and 9.0 cm from the lens.How tall is the specimen?

Accepted Answer

A) 6.8 mm 
B) 5.4 mm 
C) 1.7 mm 
D) 0.68 mm

Question 18

If a spherical concave mirror has a radius of curvature R,its focal length is

Accepted Answer

A) R/4. 
B) R/2. 
C) R. 
D) 2R. 
E) 4R.

Question 19

A light ray in glass arrives at the glass-water interface an an angle of θ = 48° with the normal.The refracted ray in water makes an angle φ = 72° angle with the normal,as shown in the figure.The index of refraction of water is 1.33.The angle of incidence is now changed to θ = 37°.What is the new angle of refraction φ in the water?

Accepted Answer

A) 50° 
B) 48° 
C) 46° 
D) 52° 
E) 54°

Question 20

An object is 10 cm in front of a concave spherical mirror with a focal length of magnitude 3.0 cm.Where is the image?

Accepted Answer

A) 13 cm from the mirror 
B) 7.0 cm from the mirror 
C) 4.3 cm from the mirror 
D) 3.3 cm from the mirror

Exam 26: Geometrical Optics