Reflection of light

Reflection occurs when a light ray bounces off a surface.

Terminology :

Incident ray is the incoming light ray.

Reflected ray is the light ray moving away from the surface .

The most important characteristic of these rays is their angles in relation to the reflecting surface. These angles are measured with respect to the normal of the surface.

The normal is an imaginary line perpendicular to the surface.

The angle of incidence, θi is measured between the incident ray and the normal.

The angle of reflection, θr is measured between the reflected ray and the normal.

When a ray of light is reflected, the reflected ray lies in the same plane as the incident ray and the normal.

Law of Reflection
The Law of Reflection states that the angles of incidence and reflection are always equal and
that the reflected ray always lies in the plane of incidence.

When you smile into a mirror, you see your own face smiling back at you. Did you notice that;
i. the size of the image is the same as you (object)
ii. the distance of the image seem as the same distance of you from the mirror.
iii. when you move your left hand, the image will move it right hand
iv. then you image never upside down .



worked example:
Question: An incident ray strikes a smooth reflective surface at an angle of 33◦ to the surface normal. Calculate the angle of reflection.

Answer
Step 1 : Determine what is given and what is required We are given the angle between the incident ray and the surface normal. This is the angle of incidence. We are required to calculate the angle of reflection.

Step 2 : Determine how to approach the problem We can use the Law of Reflection, which states that the angle of incidence is equal to the angle of reflection.

Step 3 : Calculate the angle of reflection We are given the angle of incidence to be 33◦. Therefore, the angle of reflection is also 33◦.

quiz :

Laws of reflection » Quiz Make

Physics Definition

Normally this is test in paper 2 and 3, remember to answer in full sentence DO NOT write equation !!!
example :
a. ) momentum is product of mass and velocity ( correct )
b. ) momentum = mass x velocity ( wrong)
SPM Physics Terms and Definition

Acceleration and deceleration

Dear our form 4 students answer following question before star your lesson.

Pretest:

1. state the meaning and unit for the symbol
i) a
ii) v
iii) u
iv) t

2. Define acceleration and deceleration

Lesson start:

Acceleration is the rate of change of velocity. ( 1 mark in paper 2 )

An object accelerates when it moves with increasing velocity.

An object decelerates when is getting slower, its velocity is decreasing.

Equation :

where

a: acceleration ( ms-²)

u: initial velocity ( ms-¹)

v: final velocity ( ms-¹)

t: time ( second)

Calculation:

Tips:

First of all find out all useful info as highlighted. Then substitute the info given in equation, while you are calculating check whether need to change units or not. (e.g., from km to m, hour to seconds)

email your solution to fizikf5@gmail.com

1.An athletic runs from the starting line and achieves a velocity of 12 m/s in 3 s. Find his/her acceleration. (ans: 4 ms^-2)

2. A track travels along a road with a velocity of 20 m/s the driver slam on the brake when a chicken suddenly runs across the road. Assuming the truck take 8s to complete stop from the time the driver hit the brake, determine the acceleration of the lorry. (ans: -2.5 ms^-2)

3. A motorcycle move with a velocity of 25 m/s. the motorcyclist brakes and its velocity decreases uniformly to 10 m/s in 3s. The motorcycle continues to slow down with the same acceleration until it comes to a stop. Find the time taken for the motorcycle to stop. (ans: 5s)

* Step 1 : Determine its acceleration in the first 3s,

Step 2 : Determine the time taken .

For more detail study the graph below.

Form 4 Chapter 3 Force and pressure

Simple notes and exercises with answer

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