A reflection occurs when we flip an object or shape across a line. Like a mirror, the object is exactly the same size but everything is in the opposite position. In other words, what was on the left will now be on the right and vice versa.

Have a play with the applet below. You can change the shape, the position of the shape and the direction of the line.

As you play, notice how:

every point on the object or shape has a matching point on the flipped image
both shapes are the same distance from the reflection line

Examples
Question 1
Which picture shows a reflection?

Think: Which picture looks like its been flipped- A or B?

Do: In (B), the picture is exactly the same. It has just been slid down. This means it's a translation.

In (A), the alien's spaceship has been flipped upside down! So this is the reflection.

Question 2

This picture is an example of a:

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QUESTION 3

Which image below represents the reflection for the following shape about the vertical mirror line?

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QUESTION 4

Which image below represents the reflection for the following shape about the vertical mirror line?

A shaded four-sided polygon is situated on a square grid. The whole figure is drawn on three squares on the third column of the grid. Two squares on the third column are shaded. On the square below these two, a right triangle is shaded with the hypotenuse being the line when the top left and bottom right vertex of the square is connected. The shaded square at the top of the figure is located at the second row from the top and the shaded right triangle of the figure is located at the third row from the bottom. A vertical mirror line is drawn in between the line between the fourth and fifth column.

A shaded four-sided polygon is situated on a square grid. The whole figure is drawn on three squares on the sixth column of the grid. Two squares on the sixth column are shaded. On the square above these two, a right triangle is shaded with the hypotenuse being the line when the bottom left and top right vertex of the square is connected. The shaded right triangle at the top of the figure is located at the second row from the top and the shaded square at the bottom of the figure is located at the third row from the bottom. A vertical mirror line is drawn in between the line between the fourth and fifth column.
A

A shaded four-sided polygon is situated on a square grid. The whole figure is drawn on three squares on the sixth column of the grid. Two squares on the sixth column are shaded. On the square below these two, a right triangle is shaded with the hypotenuse being the line when the top right and bottom left vertex of the square is connected. The shaded square at the top of the figure is located at the second row from the top and the shaded right triangle of the figure is located at the third row from the bottom. A vertical mirror line is drawn in between the line between the fourth and fifth column.
B

A shaded four-sided polygon is situated on a square grid. The whole figure is drawn on three squares on the sixth column of the grid. Two squares on the sixth column are shaded. On the square below these two, a right triangle is shaded with the hypotenuse being the line when the top left and bottom right vertex of the square is connected. The shaded square at the top of the figure is located at the second row from the top and the shaded right triangle of the figure is located at the third row from the bottom. A vertical mirror line is drawn in between the line between the fourth and fifth column.
C

A shaded four-sided polygon is situated on a square grid. The whole figure is drawn on two squares on the sixth column of the grid. The left half of one squares on the sixth column is shaded. On the square below this, a right triangle is shaded with the hypotenuse being the line when the point from the middle of the left side of the square is connected to the bottom right vertex of the shaded part of the square above. The shaded square at the top of the figure is located at the third row from the top and the shaded right triangle of the figure is located at the third row from the bottom. A vertical mirror line is drawn in between the line between the fourth and fifth column.
D

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