Physics- Reflection + Practical Flashcards
(18 cards)
What are Virtual images?
Mirror Images are described as Virtual images.
-The image is formed using virtual rays, formed in a location that light rays don’t actually reach (as they can’t actually pass through the back of the mirror)
-So Light rays appear to come from the image but doesn’t actually pass through it.
How are Real images formed?
Real Images are formed using actual light rays:
-the rays from the object focus together on a point to make an image
Describe the difference in the images produced by Convex lenses.
Convex mirrors (lens) produce Virtual images AND Real images.
The Real images are always inverted (upside down), appear closer to the mirror and are smaller than the object.
Its virtual images are always upright and can be magnified (larger than the object)
What type of image do Concave lenses produce?
Concave mirrors (lenses) produce Virtual images that are always Upright, diminished (smaller) and within the focal point and the lens.
What type of image do Plane mirrors produce?
Plane mirrors (lenses) form images that appear the same distance behind the mirror as the object; they are virtual, the same size as the object and laterally inverted (flipped sideways).
Describe Refraction:
Refraction occurs when a wave passes from one medium to another - the light changes direction on entering/leaving the glass block, as light travels at diff speeds in diff materials.
Refraction Q- When leaving the glass, as the angle of incidence increases…
the angle of refraction gets even larger but this can only happen up to a point.
What happens if the angle of incidence is too big?
If the angle of Incidence is too big, no refraction occurs- instead, we observe Total Internal Reflection (TIR): the light reflects within the block, and the Law of Reflection applies instead.
What is the Critical angle?
The Critical angle is the minimum angle at which TIR will occur (and Refraction no longer occurs) , the larger the refractive index of the substance, the smaller the critical angle.
Why does TIR not occur as light passes from air into glass?
As air is less dense than glass.
List two instances in which TIR can occur:
-TIR can occur more than once in the same piece of glass:
-a bike reflector is made up of many units-
-Cats’ eyes in the road
What are Optical Fibres?
Optical Fibres are very thin, flexible, transparent fibres than light can pass through by TIR.
How are optical fibres used?
As well as decorative items, optical fibres are mostly used for communications- light (visible or infrared) flashes on and off in binary code to transfer data quickly.
Usually, each ‘bundle’ contains many fibres, so many data can be sent at the same time.
What is an endoscope and how does it use optical fibres?
An endoscope is a flexible camera that can be inserted into the body to take images from within.
Some of the fibres illuminate the area, while others carry the signal back to the computer; small tools can also be attached for simple procedures.
Write the Method for the Required
The aim of this exp is to investigate the Law of Reflection, demonstrating that you can take accurate measurements.
Safety Warning: Please remember that the ray box will get hot- switch off when not in use.
-Graph paper
-Sharp Pencil
-Ruler
1) Draw a straight line across the middle of the page (to represent the mirror). Halfway along the line, draw a perpendicular line (the normal line)
The point at which these lines meet is the ‘point of reflection’.
2) Draw lines from the point of Reflection, away from the mirror, at angles of 10 degrees to 80 degrees, at 10 degree intervals.
-These lines will represent the pathways taken by the incident light ray in each exp- the angles you measured represent the angle of incidence.
Use protractor to draw angles from the normal line
3) Place the mirror on the graph paper, so its reflective surfaces follows the mirror line on the paper
4)Set up your ray box to transmit a single ray of light. Direct the ray along the 10degree pathway, so that the light reflects in the mirror at the point of reflection
5)Using your pencil, mark the two positions along the reflected ray. Remove the mirror, and draw a straight line from the point of reflection through your two marks.
6)Measure the angle of reflection (the angle made between the reflected ray and the normal line.
7) Repeat the experiment, with the light ray following the other incident pathways.
What is the Angle of Incidence?
The angle between the normal and incident ray
What is the Angle of Refraction?
he angle between a refracted ray and the normal drawn at the point of incidence to the interface at which refraction occurs.
