The Academic Curriculum - Rays and Waves
In this section, I'm going to explain the basic (and maybe a bit advanced) principles of rays and waves.
This section is confusing at first, but it gets much easier when you know the basics by heart.
This section is confusing at first, but it gets much easier when you know the basics by heart.
The Academic Curriculum - Rays (the very basics, straight from the textbook)
To begin with, what is 'seeing?' You cannot see in the dark. You obviously cannot see with your eyes closed, or something blocking your sight.
Therefore, we can deduce that 'seeing' involves light coming into your eyes.
The act of 'seeing things' is your eye intercepting the light that bounces off the surface of various objects.
Lamps, lightbulbs, TV, the sun..... these are luminous, and the light that is emitted from them touches the surface of non-luminous objects and are reflected back into your eyes. Your eyes then processes these light signals and sends a message to your brain, which in turn visualizes the image that you 'see.'
The best way to visualize this is to think of lights as rays coming off in all directions
The color of the object you are seeing depends on what colors they reflect, and what they absorb.
The color depends on what signals you get from your eye. If you get red light coming from that object, you will percieve it as red.
But to get 'red light' from that object, the red light has to be reflected from the object.
However, a normal light contains red, green and blue colored lights that, when mixed together, becomes white.
To get only red light reflected, the blue and green has to go somewhere, right? So the object absorbs them, leaving only red free to reflect.
And that is how you see colors.
Features of Light
Light is a form of radiation. It means that light radiates(spread out) from its source. They are often shown as rays, which is a line starting out from a dot.
Light travels in straight lines. Like you don't know this already.
Light transfers energy. When you bask in the sun, you get warm. That's because light carries energy with it. You need energy to make light. That energy goes somewhere.
Light is the fastest thing known to man, as of now. The speed of light is 3 * 10^9 meters per second. Nothing that we know of can travel faster than this.
Therefore, we can deduce that 'seeing' involves light coming into your eyes.
The act of 'seeing things' is your eye intercepting the light that bounces off the surface of various objects.
Lamps, lightbulbs, TV, the sun..... these are luminous, and the light that is emitted from them touches the surface of non-luminous objects and are reflected back into your eyes. Your eyes then processes these light signals and sends a message to your brain, which in turn visualizes the image that you 'see.'
The best way to visualize this is to think of lights as rays coming off in all directions
The color of the object you are seeing depends on what colors they reflect, and what they absorb.
The color depends on what signals you get from your eye. If you get red light coming from that object, you will percieve it as red.
But to get 'red light' from that object, the red light has to be reflected from the object.
However, a normal light contains red, green and blue colored lights that, when mixed together, becomes white.
To get only red light reflected, the blue and green has to go somewhere, right? So the object absorbs them, leaving only red free to reflect.
And that is how you see colors.
Features of Light
Light is a form of radiation. It means that light radiates(spread out) from its source. They are often shown as rays, which is a line starting out from a dot.
Light travels in straight lines. Like you don't know this already.
Light transfers energy. When you bask in the sun, you get warm. That's because light carries energy with it. You need energy to make light. That energy goes somewhere.
Light is the fastest thing known to man, as of now. The speed of light is 3 * 10^9 meters per second. Nothing that we know of can travel faster than this.
The Academic Curriculum - Reflection in Mirrors
There are two laws of reflection. And these apply to all types of mirrors, whether they are flat or converse.
1. The angle of incidence is equal to the angle of reflection (i = r)
2. The incident ray, the reflected ray, and the normal ray all lie in the same plane.
I will explain number 1 in a picture (Diagram 1)
1. The angle of incidence is equal to the angle of reflection (i = r)
2. The incident ray, the reflected ray, and the normal ray all lie in the same plane.
I will explain number 1 in a picture (Diagram 1)
As you can see above, the angle of incidence (the angle of light coming inside) is always equal to the angle of reflection (the angle of light going outwards).
While the terminology might not seem so important (it isn't, as long as you can recognize what it means on tests), the theory is crucial in this chapter.
Take a look at the diagram below.
While the terminology might not seem so important (it isn't, as long as you can recognize what it means on tests), the theory is crucial in this chapter.
Take a look at the diagram below.
![Picture](/uploads/2/3/0/8/23088688/4593237.jpg?378)
This diagram might not be so easy to understand at first, but once you get the hang of it, you can apply the basic theory here to most of the questions you see. Basically, picture that there are thousands and millions of light rays reflected off the tip of the object. And picture one ray, out of all those lights, that comes into the uppermost part of your eye, and another that comes into your lowest part. Those two rays are what will decide the outcome of the reflection.
Draw those two rays that you pictured, like the diagram on the left. Now, extend them so that they converge at one point behind the mirror. That converging point is where the reflected image exists virtually.
Imagine another 'world' behind a mirror, a world where everything is just like the real world, but backwards. And in this virtual world, the reflected object exists in the same distance from the mirror as the actual object. If you visualize it this way (I know it's not great, but it is how I learned it), understanding the theory could be a bit easier.
Draw those two rays that you pictured, like the diagram on the left. Now, extend them so that they converge at one point behind the mirror. That converging point is where the reflected image exists virtually.
Imagine another 'world' behind a mirror, a world where everything is just like the real world, but backwards. And in this virtual world, the reflected object exists in the same distance from the mirror as the actual object. If you visualize it this way (I know it's not great, but it is how I learned it), understanding the theory could be a bit easier.
How to sketch reflections correctly
In both your tests and problems, there will be at least one problem in which you have to sketch the position, the size, and the direction of an object's reflection correctly. It is difficult, and many people have problems solving these type of questions. I have a video (made by Mr. Guay Hansen, not me) from youtube which could help you with this.
In both your tests and problems, there will be at least one problem in which you have to sketch the position, the size, and the direction of an object's reflection correctly. It is difficult, and many people have problems solving these type of questions. I have a video (made by Mr. Guay Hansen, not me) from youtube which could help you with this.
Link : http://youtu.be/jAvZqJE95SQ
The Academic Curriculum - Refraction of Light (from textbook)
Refraction happens where a light (or a wave) travels through two different mediums of different density. Like travelling from air into water.
In these cases, light bends accordingly to whether it travels from light density to heavy density, or heavy density to light density.
When it travels from light to heavy density, it bends inwards. When travelling from heavy to light density, it bends outwards.
(See diagram 3 for a better explanation)
In these cases, light bends accordingly to whether it travels from light density to heavy density, or heavy density to light density.
When it travels from light to heavy density, it bends inwards. When travelling from heavy to light density, it bends outwards.
(See diagram 3 for a better explanation)
Depending on what the medium is, the angle of refraction can change even when the angle of incidence stays the same.
The refractive index measures this, so that refractive index = speed of light in vaccum/speed of light in medium
Glass, for example, has a refractive index of 1.52, so we can deduce that the speed of light in glass is *only* 200 000 km/s.
Refraction can be used in another way that might not be so obvious: rainbow.
When you shine a white light on a prism, you will see 7 different colors coming out (a spectrum actually).
This is because a prism refracts different colored lights by different amounts (this is called deviation).
Red light is deviated the least, while violet light is deviated most by a prism.
The difference is very slight, but most diagrams exaggerate the difference, to show the spectrum clearly.
The important thing is to remember the direction the light bends to.
The refractive index measures this, so that refractive index = speed of light in vaccum/speed of light in medium
Glass, for example, has a refractive index of 1.52, so we can deduce that the speed of light in glass is *only* 200 000 km/s.
Refraction can be used in another way that might not be so obvious: rainbow.
When you shine a white light on a prism, you will see 7 different colors coming out (a spectrum actually).
This is because a prism refracts different colored lights by different amounts (this is called deviation).
Red light is deviated the least, while violet light is deviated most by a prism.
The difference is very slight, but most diagrams exaggerate the difference, to show the spectrum clearly.
The important thing is to remember the direction the light bends to.