Lens Basic resentation by Vicente & Lourdes S.

https://drive.google.com/file/d/0B-1zyIDIorqVdzVQSHFxOWZiQk0/edit?usp=sharing 

Natalia and Andrea's lens presentation

Timeline

http://www.tiki-toki.com/timeline/entry/207949/timeline/#vars!date=1621-01-01_10:01:28!

Waves exercises

Waves

A wave is a disturbance that carries energy from one place to another.

Matter is NOT carried with the wave! A wave can move through matter (a “medium”). If it must have a medium, it is called mechanical wave. If it can travel without a medium (such as in space), it is called electromagnetic wave.

Wave Types

1.      Transversal waves: Waves in which the medium moves at right angles to the wave direction.

Parts of a transverse wave:

Crest: the highest point of the wave

trough: the lowest point of the wave

2.      Compressional (longitudinal) wave: Waves in which the medium moves back and forth in the same direction as the wave.

Wave properties depend on what type of energy makes the wave.

1.      Wavelenght: The distance between one point on a wave and the exact same place on the next wave.

2.      Frequency: How many waves go past a point in a second; measured in hertz (Hz). The higher the frequency, the more energy in the wave.

3.      Amplitude: How far the medium (crests and troughs, or compressions and rarefactions) moves from the line of origin (the place the medium is when not moving). The more energy a wave carries, the bigger its amplitude.

4.      Wave speed: Depends on the medium the wave is traveling in. This varies in solids, liquids and gases.

            Equation for calculating wave speed:

            wave speed = wavelencht (in m) x frequency (in Hz)

Problem:

If a wave has a wavelength of 2 m and a frequency of 500 Hz, what is its speed? Answer: wave speed  =1.000 m / second

Parts of the Wave

Worksheet

Parts of a Wave

.

Part 1

 

In the diagram below, identify the parts of a wave and then give a definition of each term

.

Crest / trough / line of origin / wavelength / amplitude 

 

crest = 5 (  the highest point of the wave)               
trough = 2 (the lowest point of the wave)   
line of origin= 1 (mean position of the particles)     
wavelength= 3 (The distance between one point on a wave and the same place on the next wave)
amplitude=4 (The distance between the crest or the trough and the line of origin)

Part 2

 

State which of the following waves you think has the highest frequency and which might have the lowest frequency. Explain the reasons for your selections.

wave #	crest	Trough	wavelength
1	1 cm	1 cm	2 cm
2	3.5 cm	3.5 cm	2.5 cm
3	.5 cm	.5 cm	3 cm
4	2 cm	2cm	.5 cm

(Perhaps it would be useful for you to draw, on graph paper, the four different waves )

The highest frequency is the Wave number 1 and the lowest frequency is the wave number 4, because the frequency and wavelength are inversely proportional.

Waves

1.  What are waves?

 Waves are disturbences that transport energy from one location to another without tranportation of matter.

2.   What are mechanical waves?

They are waves that require a material medium to propagate from one point to another.

3.   Why can waves propagate?

Mechanical waves can propagate because of the interaction forces between particles of a medium.

4.   In the 'spring model', What do the springs represent?

The spring represents the interaction forces between particles.

5.  Can you specify two different types of mechanical waves?

There are transverse waves and longitudinal waves.

6.  Can you define both kinds of waves?

 Transverse waves make the particles of a medium vibrate perpendicular to the direction of the wave motion.

Longitudinal waves make the particles of a medium vibrate parallel to the direction of the wave motion.

7.   What is 'inertia'?

It's the tendency of objects to resist change in motion when pushed or pulled.

8.  What kind of particles tend to have more inertia?

Particles with greater mass have more inertia

9.   In longitudinal waves, are the particles of the medium carried along by the propagating waves?

The particles of the medium are not carried along by the propagating waves

10. In longitudinal waves, why don't the particles of the medium move at the same time?

Because they have inertia

 

Maths's problems

0'856 = 0'9

We are going to round off to tenth. When the next decimal is greater than or equal to five, we round up. In our example, the next decimal is 5, so we put 9 in tenth.

a^4 · a^6 = a^(4+6) = a^10

"a" to de power 4 multiplicated by "a" to the power 6 equals "a" raised to the addition of 4 plus 6. The result is "a" to the power 10.

7/5 : 3/8 = 56/15

Here we have to multiply in cross: We multiplied 7 (the numerator of the first fraction) times 8 (the denominator of the second fraction) and the result (56) is the numerator of the new fraction. And for getting the denominator of the result fraction, we have to multiply 5 times 3 (equals 15).