Teacher: A.McDonnell

Formation of Images�- Concave Mirror

C

F

P

Principal Axis

f

Today, we are going to examine how images are formed in concave mirrors. We will also learn how to locate the position of these images.

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To do:

• Rules of reflection for concave mirrors
• Locate the image by drawing rays

�

Object

Image

Starter to Engage:�Look at the concave mirrors in front of you. List some advantages and practical uses for concave mirrors.

**Animations work when in present mode

Rule One:

F

C

P

A ray of light coming in parallel to the principal axis is reflected back through the focus.

Rule Two:

F

C

P

A ray of light passing through the focus comes back parallel to the axis.

Rule Three:

F

C

P

A ray of light passing through the centre of curvature is reflected back along its own path.

Rule Four:

F

C

P

A ray which strikes the pole is reflected at an equal angle with the axis.

Explore - Locate the images of the following objects using the rules given.

F

F

F

F

C

C

C

C

Explore - Locate the images of the following objects using some of the rules given.

F

F

F

F

C

C

C

C

o

o

o

o

i

i

i

Parallel Rays

Diverging Rays

Explore - Visit www.scoilnet.ie to interact with the animation. � Change the location of the object. Record the characteristics of the image using this activity sheet.

Explain - Look into the concave mirrors on your desk to observe the following...

F

F

F

F

C

C

C

C

i= Real image � Same size as object� Inverted

i= Real image � Magnified� Inverted

i= Image at infinity

i= Virtual image � Magnified� Upright

Use:�Shaving/Make-up Mirror

Use: Floodlights

Use: Watch Magic Trick here

Object at C

Object between F and C

Object at F

Object inside F

Elaborate:

F

C

P

An object of height �4 cm is placed 18 cm in front of a concave mirror of focal length 8cm.��Using ray diagrams locate the image formed by the concave mirror.

Note: 2|PF| = |CP|

o

i

i= Real | Inverted� Magnified | Diminished� Upright | Inverted

Scale: 1 box represents 1 cm

Evaluate: