Lights and Optics

Question 1

Boundary of visible spectrum?

Answer 1

380 to 750nm

Question 2

Law of Reflection

Answer 2

Question 3

Plane Mirror

Answer 3

-creates a virtual image

Question 4

T/F: Plane Mirror always produce virtual images.

Answer 4

True

Question 5

Real vs. Virtual Image

Answer 5

Real image: light converge at the position of the image
Virtual image: light does not converge at the position of the image

Question 6

An object is placed 7 cm in front of a concave mirror that has a 10cm radius of curvature. Determine the image distance, the magnification, whether the image is real or virtual and whether if it is inverted or upright.

Answer 6

Use equation:
1/f = (1/o) + (1/i) = 2/r
(r = radius of curvature)
–> 1/i = 2/r - 1/o
—> 1/i = 2/10 - 1/7
—> 1/i =4/70 cm ==> i = 17.5 cm
–> (+) i indicates that the image is real
(2) magnification: m = -i/o
–> m = -17.5 cm / 7cm = -2.5
–> a (-) m indicates that it is inverted; it is magnified by a power of 2.5

Question 7

What is the equation for the magnification of mirror? What does a -m indicate?

Answer 7

m = - i/o; a negative m indicates that the image is inverted.

Question 8

If abs(i) is greater than abs(o), what does it indicates?

Answer 8

The object is magnified

Question 9

For an object that is placed in the focal point of a concave mirror, what type of image is formed?

Answer 9

No image will be formed.

Question 10

For an object that is placed in between the focal point and center of curvature(C)of a concave mirror, what type of image is formed?

Answer 10

a inverted, magnified, real image

Question 11

For an object that is placed in between the focal point and the mirror of a concave mirror, what type of image is formed?

Answer 11

an upright, magnified, and virtual image

Question 12

For an object that is placed any distance in front of a convex mirror, what type of image is formed?

Answer 12

It is always virtual, upright, and reduced.

Question 13

An inverted image is always ______, while an upright image is always ______.

Answer 13

real; virtual

Question 14

How to calculate the index of refraction n?

Answer 14

n = c/v
-c = speed of light in the vacuum (3.0 x 10^8 m/s)
v= speed of light in the medium

Question 15

(1)Give the equation for Snell’s Law
(2)How does the angle of the light change as it moves to a medium with a lower n value?

Answer 15

it would bend away from the normal

Question 16

What will the angle of refraction be if a light ray travels from water to air at an angle of 45 degrees to the normal?
A.Greater than 45 degrees
B.Less than 45 degrees
C.45 degrees
D.There will be no refraction

Answer 16

A; bc n of air is smaller than n of water –> light ray will bend away from the normal

Question 17

What is the equation for calculating total internal refraction?

Answer 17

Question 18

Compare and contrast concave and convex lenses.

Answer 18

-both with 2 focal points

Question 19

List the sign convention for the lenses:
-o
-i
-r
-f
-m

Answer 19

Question 20

An object is 10 cm to the left of converging lens with a 20 cm focal length. Find where the image is formed, if it is upright or inverted, and if it is real or virtual.

Answer 20

Question 21

Optometrist often describe a lens in term of its ______, which is measured in _______. It is given by the equation _______.
People who has myopia need ____ lens.
power; diopters; P =1/f (f is measured in meter)

Answer 21

power; diopters; P =1/f (f is measured in meter)
-converging

Question 22

What is the difference between the lenses that are in contact in a multiple lens system and lenses that are not in contact in a multiple lens system?

Answer 22

-for lenses in contact (ex: contact lenses) –> the system is viewed as a single lens
-for lenses not in contact (the image from one lens would become the object of another.

Question 23

Single-slit diffraction
1.what happens to the central maxima when the slit becomes narrower?

Answer 23

It becomes wider

Question 24

Monochromatic red light is allowed to pass between two different media. If the incident angle in medium 1 is 30 degrees and the incident angle in medium 2 is 45 degree, what is the relationship between the speed of light in medium 2 compared to medium 1?

Answer 24

n1sin(angle 1) = n2sin(angle 2)
and n = c/v
–> (c/v1)(angle 1) = (c/v2)(angle 2)
–>(1 / v1)(1/2) = (1/ v2)(1/ (2)^(1/2))
–> v2 = v1(2)^(1/2)

Question 25

Which of the following can split lights into its components?
I. dispersion through a prism
II. Diffraction through a grating
III.Refraction within a thin film
IV. Reflection from an ideal convex mirror

Answer 25

I,II,and III

Question 26

If an object produced by the lens appears to be very close to the focal point, then the object must be?

Answer 26

far from the lens
bc 1/o ~ 0

Question 27

Which of the following correctly describes the image produced by a plane mirror?
A.The image is real and upright.
B.The image undergoes vertical inversion.
C.The image will move twice as fast towards the plane of the mirror as the object moves.
D.The image is the same size as the object with no lateral inversion.

Answer 27

Answer: C
The image is virtual and upright since the image appears where the light rays project back upon reflection.
Hint #2
The image is not vertically, but it is inverted laterally.
Hint #3
The image is the same size as the object, but with lateral inversion.
Hint #4
The image will appear to move twice as fast as the object. As instance, if a person is standing 2 meters from the mirror, then the image appears to be 4 meters from the person. For the two to come together, the person travels 2 meters, while the image appears to travel 4 meters in the same time period