Chapter 17.2- The interference of light

Question 1

What is interference?

Answer 1

When waves interact

Question 2

What is constructive interference?

Answer 2

When the inference of waves leads to a larger amplitude

Question 3

What is destructive interference?

Answer 3

When the interference of waves leads to a smaller or even zero amplitude

Question 4

What do we use to create light scenarios where we see diffraction patterns?

Answer 4

Very small slits and ray beams

Question 5

What do we use to create light scenarios where we can see the interference of light?

Answer 5

We have to use double slits and a ray of light

Question 6

What are double slits?

Answer 6

Two long narrow slits that are close together. Used to see interference of light

Question 7

What do double slits do when light is seen through them?

Answer 7

The light spreads out behind each slit. The two spreading waves of light overlap in the region between the slits and the screen

Question 8

Where does constructive interference occur?

Answer 8

When the distances between r1 and r2 differ by JUST a WHOLE NUMBER of wavelengths

Question 9

Where does destructive interference occur?

Answer 9

When the distances between r1 and r2 differ by a whole number of wavelengths AND A HALF

Question 10

What is m

Answer 10

m is just an integer used to measure the difference of wavelengths

Question 11

What will we see for constructive interference?

Answer 11

The intensity of light to be high

Question 12

What will we see for destructive interference?

Answer 12

For these positions on the screen to be completely dark

Question 13

What are interference fringes?

Answer 13

A series of alternating bright and dark bands

Question 14

What is the central maximum?

Answer 14

When m = 0 and it is the brightest fringe. It is the midpoint of the viewing screen.

Question 15

Geometry of the double-slit interference:

What is d

Answer 15

The spacing between the two slits

Question 16

Geometry of the double-slit interference:

what is L

Answer 16

The distance to the viewing screen

Question 17

Geometry of the double-slit interference:

What do we assume in relation between L and d

Answer 17

We assume that L is MUCH LARGER than d

Question 18

Geometry of the double-slit interference:

How do we calculate change in r besides the obvious way

Answer 18

Multiply the integer thing, m, by lambda. IF ITS CONSTRUCTIVE INTERFERENCE.

Question 19

Geometry of the double-slit interference:

How do we find the specific positions not the screen where constructive interference occurs and change in r = m(lamda)

Answer 19

Y = L tan theta

Question 20

Geometry of the double-slit interference:

What is P

Answer 20

The distance of r1 from one slit and r2 from the other slit

Question 21

Geometry of the double-slit interference:

How can we calculate point P

Answer 21

By either finding y or by finding angle theta

Question 22

Geometry of the double-slit interference:

What is y

Answer 22

Distance from the center of the viewing screen

Question 23

Geometry of the double-slit interference:

How can we find y

Answer 23

y = L tan theta

y = (m lambda L / d )

Question 24

Geometry of the double-slit interference:

Because the screen is very far away compared to the distance between the two slits what are the two things we can assume

Answer 24

1. That the two paths to point P are virtually parallel

2. Because they are parallel, we can make a small right triangle who has angle theta

Question 25

Geometry of the double-slit interference:

What is the path length difference between the two waves

Answer 25

The short side of the small right triangle.

Question 26

Geometry of the double-slit interference:

What is theta m

Answer 26

Angle theta of bright fringes

Question 27

Geometry of the double-slit interference:

What is y’m

Answer 27

The mth minimum

Question 28

Geometry of the double-slit interference:

What is ym

Answer 28

The mth maximum

Question 29

Geometry of the double-slit interference:

What did you get confused about on example 17.2

Answer 29

I thought that when it said a bright fringe is observed at 9.5 mm that it was r1. But it wasn’t I needed to plug it into equation 17.8 for bright fringes