Reflection of light occurs when light changes direction as it bounces off a surface. Reflection can be classified into two. They are
- Regular Reflection
- Irregular Reflection
Regular Reflection
This is the reflection that occur on a smooth surface such as plane mirror, clean water etc. Regular Reflection is also called Specular Reflection.
Irregular Reflection
This is the reflection that occur on rough surface such as paper, cloth, table etc. Irregular Reflection is also called scattered or diffused Reflection.
Laws of Reflection
These laws states that
- The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane.
- The angle of incidence is equal to the angle of reflection.
Images
When you look at yourself in a mirror, what is formed in that mirror is called an image. An Image can be classified into two.They are;- Real Image
- Virtual Image
Real Image
This is one which rays of light pass. If a screen is placed at the position of a real image. It can be seen on the screen. The image formed on a pinhole camera is a real image. A Real image is formed in front of a mirror.
Virtual Image
This is the one in which rays of light do not reach but nevertheless visible to the eyes. The image formed by a plane mirror is virtual. A virtual Image is formed behind the mirror.
Characteristics of an image formed by a plane mirror
- It has the same size as the object. i.e its magnification is one.
- It is virtual.
- It is upright or erect.
- It is laterally inverted.i.e
Uses of a plane mirror
- The common looking glass is a plane mirror.
- It is employed in a pointer instrument such as ammeter, voltmeter etc
- It is used to construct a sextant ( an instrument used to measure the angle of elevation of the sun)
- It is use to construct simple periscope by placing two parallel mirrors at angle 45°.
- It is used to construct a toy called kaleidoscope by inclining two plane mirrors at an angle 60° to each other.
Inclined Mirrors
When mirrors are inclined at an angle to each other, numbers of images are produced which depends on the angle of inclination. The smaller the angle of inclination, the higher the number of images produced.i.e
Examples
- Calculate the number of images produced when two plane mirrors are inclined at an angle 60° to each other
Solution
- Determine the number of images produced by two perpendicular mirrors.
Solution
- Determine the number of images produced in a barber's shop having two parallel mirrors
Solution
The answer to the question is infinity ( The reason why the answer is infinity is because, when two mirrors are parallel to each other, multiple number of images are seen).
- A ray of light makes an angle of 35° with a plane mirror. What is the angle of reflection?
Solution
- In the figure below, what is the angle of reflection of the ray of light in mirror 2
Solution
- Two mirrors of the same length are arranged as shown in the diagram below. A ray of light NO strikes the system at O and emerges along PQ. The emergent ray has been deviated through?
Solution
