Some of my students are learning this chapter in school. So decided to do some notes for them.

Well… but nothing is free! hee hee.

Ifah, Jas T, Jessie: Please find time to read through and digest the notes. There will be a short quiz on this topic this week. 🙂

Light

· Denser Medium. Light Ray bends towards the normal.

· Angle of refraction, incidence is the angle that the ray makes with the normal not the medium.

· All normal, incidence ray, refraction ray must be on the same plane.

· If 90 degrees to the plane ( aka parallel to the normal) There is no refraction angle. It will be a straight line into the medium.

· Concave – magnify things ( like microscope, dentist mirror, cosmetic mirror).

· Convex – shows smaller, wider view of objects ( Shops corner mirror, bend mirror, car mirror).

· Light ray can be transformed to other forms of energy and follows energy law of conservation.

I believe the most difficult part of Light topic is the drawing of the reflected and refracted image. A lot of my student dreaded this part. 🙁

But hey, its not difficult just a little troublesome. Dont let a troublesome thing get in your way of getting marks.

· In drawing refracted image,

o Object should be starting point, not the eye.

( TIP: You can try drawing the refracted image first which will be ABOVE the real object. Then draw 2 dotted lines to the water surface. At the points where the dotted lines meets the water surface, draw the 2 normal respectively. Then draw BOLD lines back to the object.) (The same steps can be used for reflected image drawing. Just that the real object is located at the opposite side (unlike refraction case. )

o Image should have dotted lines.

o There must be 2 or more rays

o Must add arrows to the lines ( Only for BOLD lines. The dotted lines have no arrows)

o Rays must be towards eyes

o Must draw normal ( perpendicular to the plane) in dotted lines too

o Above the water, extend straight (full line) from the dotted lines of IMAGE to the eyes. (This is the refracted ray not incident ray).

 

 

Colour

Rainbow colours _ ROY G BIV ( This name can be used to remember the sequence of the colour in a rainbow)

Refraction of white light cause dispersion of white light in 7 colours. A prism can be used to show that.

Noted angle of refraction: red > orange > yellow > green > blue > indigo > violet

Another area that will be tested for colours is the colour of the object with different colour light shone on the object. Note Primary Colours and Secondary colours.

When you encounter questions on what colour will the object appear under different lights. Follow the flow chart below!! 🙂