Reflections Wjec-Eduqas Foundation

Reflections

What is a reflection?

• A reflection flips a shape across a mirror line

  • This is called the line of reflection

• The reflected image is the same size as the original object

  • It has been flipped across the mirror line to a new position and orientation

• The following two distances will be equal for each point:

  • The perpendicular distance between the original point and the mirror line 

  • The perpendicular distance between the reflected point and the mirror line

• Any points that are on the mirror line do not move

  • These are called invariant points

How do I reflect a shape?

• STEP 1
  Draw the line of reflection

  • This will usually be a vertical line () or a horizontal line ()

  • A diagonal line will either be  or 

• STEP 2
  From each vertex on the original object measure the perpendicular distance to the mirror line

  • You can usually do this by counting squares on the grid

  • If the line is diagonal then count the diagonals of the squares

• STEP 3

  Find the reflected point by measuring the same distance in the same direction from the point on the mirror line

• STEP 4
  Join together the reflected points and label the reflected image

How do I reflect a shape when the line of reflection goes through the shape?

• You follow the same steps as above

• Part of the shape gets reflected on one side of the mirror line, and the other part gets reflected on the other side

How do I describe a reflection?

• To describe a reflection, you must:

  • State that the transformation is a reflection

  • Give the mathematical equation of the mirror line

• To find the equation of the reflection line:

  • Horizontal lines are of the form <img alt=”y equals k” data-mathml='<math ><semantics><mrow><mi>y</mi><mo>=</mo><mi>k</mi></mrow><annotation encoding=”application/vnd.wiris.mtweb-params+json”>{“language”:”en”,”fontFamily”:”Times New Roman”,”fontSize”:”18″,”autoformat”:true}</annotation></semantics></math>’ height=”22″ role=”math” src=”data:image/svg+xml;charset=utf8,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20xmlns%3Awrs%3D%22http%3A%2F%2Fwww.wiris.com%2Fxml%2Fmathml-extension%22%20height%3D%2222%22%20width%3D%2238%22%20wrs%3Abaseline%3D%2216%22%3E%3C!–MathML%3A%20%3Cmath%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3Ey%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmi%3Ek%3C%2Fmi%3E%3C%2Fmath%3E–%3E%3Cdefs%3E%3Cstyle%20type%3D%22text%2Fcss%22%3E%40font-face%7Bfont-family%3A’math17f39f8317fbdb1988ef4c628eb’%3Bsrc%3Aurl(data%3Afont%2Ftruetype%3Bcharset%3Dutf-8%3Bbase64%2CAAEAAAAMAIAAAwBAT1MvMi7iBBMAAADMAAAATmNtYXDEvmKUAAABHAAAADRjdnQgDVUNBwAAAVAAAAA6Z2x5ZoPi2VsAAAGMAAAAsmhlYWQQC2qxAAACQAAAADZoaGVhCGsXSAAAAngAAAAkaG10eE2rRkcAAAKcAAAACGxvY2EAHTwYAAACpAAAAAxtYXhwBT0FPgAAArAAAAAgbmFtZaBxlY4AAALQAAABn3Bvc3QB9wD6AAAEcAAAACBwcmVwa1uragAABJAAAAAUAAADSwGQAAUAAAQABAAAAAAABAAEAAAAAAAAAQEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACAgICAAAAAg1UADev96AAAD6ACWAAAAAAACAAEAAQAAABQAAwABAAAAFAAEACAAAAAEAAQAAQAAAD3%2F%2FwAAAD3%2F%2F%2F%2FEAAEAAAAAAAABVAMsAIABAABWACoCWAIeAQ4BLAIsAFoBgAKAAKAA1ACAAAAAAAAAACsAVQCAAKsA1QEAASsABwAAAAIAVQAAAwADqwADAAcAADMRIRElIREhVQKr%2FasCAP4AA6v8VVUDAAACAIAA6wLVAhUAAwAHAGUYAbAIELAG1LAGELAF1LAIELAB1LABELAA1LAGELAHPLAFELAEPLABELACPLAAELADPACwCBCwBtSwBhCwB9SwBxCwAdSwARCwAtSwBhCwBTywBxCwBDywARCwADywAhCwAzwxMBMhNSEdASE1gAJV%2FasCVQHAVdVVVQAAAAEAAAABAADVeM5BXw889QADBAD%2F