Real and virtual images Revision Notes for AQA GCSE Physics

Real and virtual images

Images created by lenses can be either real or virtual. The type of image depends on what lens you use and where you place the object.

What are real images?

A real image is one that can be shown on a screen. Convex lenses create real images when the object is placed beyond the focal point.

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Key features of real images:

They appear upside down
They can be projected onto a screen
Their size depends on how far the object is from the lens
They get smaller when the object is very far away

When you move an object closer to a convex lens, the real image becomes larger and moves further away from the lens. However, the image stays upside down.

What are virtual images?

A virtual image cannot be shown on a screen. It appears to be where the light seems to come from, but the light rays don't actually meet there.

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Key features of virtual images:

They appear the right way up
They cannot be projected onto a screen
They appear larger than the object
They form when the object is very close to a convex lens

When do you get virtual images?

You get virtual images in two situations:

When an object is placed between a convex lens and its focal point
Always when using a concave lens (no matter where you put the object)

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Remember that concave lenses always produce virtual images, regardless of where you place the object. This is a key difference from convex lenses.

Magnification

Magnification tells you how much bigger or smaller an image is compared to the object.

Formula: $\text{magnification} = \frac{\text{image height}}{\text{object height}}$

What the numbers mean:

Magnification greater than 1 = image is larger than the object
Magnification less than 1 = image is smaller than the object
Magnification equal to 1 = image is the same size as the object

For example, if magnification = 3, the image is 3 times bigger than the object.

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Worked Example: Calculating Magnification

An object is 2 cm tall and creates an image that is 6 cm tall.

Step 1: Identify the values

Object height = 2 cm
Image height = 6 cm

Step 2: Apply the formula $\text{magnification} = \frac{\text{image height}}{\text{object height}} = \frac{6}{2} = 3$

Step 3: Interpret the result Since magnification = 3 > 1, the image is 3 times larger than the object.

Key differences between real and virtual images

Real images	Virtual images
Upside down	Right way up
Can be shown on screen	Cannot be shown on screen
Made by convex lens (object beyond focal point)	Made by convex lens (object closer than focal point) or concave lens
Can be larger or smaller than object	Usually larger than object

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Key Points to Remember:

Real images are upside down and can be projected on a screen
Virtual images are the right way up but cannot be projected on a screen
Convex lenses can make both real and virtual images depending on object position
Concave lenses always make virtual images
Magnification = $\frac{\text{image height}}{\text{object height}}$ tells you if the image is bigger or smaller than the object

Real and virtual images (AQA GCSE Physics): Revision Notes