Optical mouse

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Quick Questions

Shade in the A or B circle for each question.

1. How does an optical mouse detect movement?

A A sensor takes rapid pictures of the surface and compares them

B A rubber ball rolls and turns two rollers inside the mouse

2. Which light source is found under an optical mouse?

A A light bulb

B An LED or laser

3. True or false: an optical mouse has a moving ball underneath.

A True - the ball turns as the mouse moves

B False - it has no ball

4. What does the image sensor in an optical mouse do?

A Takes many images of the surface every second to work out distance and direction

B Records the user's voice to work out where to move the pointer

5. What happens to the movement data the mouse works out?

A It is sent to the computer, which moves the pointer on the screen

B It is printed out as a document

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1optical mouse		AAn input device that lights the surface with an LED or laser and uses a sensor to track movement
2image sensor		BThe buttons and scroll wheel send clicks and scrolling to the computer. The image sensor tracks the movement.
3The mouse lights the surface under it with an LED or laser so the sensor can see the surface clearly		CThis describes an older ball mouse. An optical mouse has no ball and uses an LED or laser and an image sensor instead.
4Unlike older mice, an optical mouse has no moving ball inside it to track movement		DLED or laser light
5An optical mouse tracks movement using a rolling ball under it		EA tiny camera chip that takes rapid pictures of the surface so changes in the image show the mouse movement
6The scroll wheel and buttons on an optical mouse track the movement of the mouse		Fno ball

Definitions

optical mouse

Fill in the Blanks

Complete each line of code by filling in the missing parts.

led ← __

image ← _______(sensor)

dx ← newX _ oldX

IF leftButton = PRESSED ____ SEND("click") ENDIF

SEND(dx, dy) TO computer ____(pointer, dx, dy)

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A LED lights the surface

B sensor takes one image only

C compare image with last image

D send movement to computer

Question 2

A LED shines light on the desk

B sensor captures images

C compare with previous image

D send ball turns to computer

E computer moves the pointer

Question 3

A ball rolls on the surface

B sensor takes rapid pictures

C movement sent to computer

D pointer moves on screen

Question 4

A user presses left button

B mouse sends no signal

C computer selects the item

Question 5

A user turns the scroll wheel

B mouse detects the turn

C mouse sends scroll signal

D the pointer changes colour

Answer Key

Optical mouse

Section A: Quick Questions

A — A sensor takes rapid pictures of the surface and compares them

B — An LED or laser

B — False - it has no ball

A — Takes many images of the surface every second to work out distance and direction

A — It is sent to the computer, which moves the pointer on the screen

Section B: Match the Pairs

optical mouse → An input device that lights the surface with an LED or laser and uses a sensor to track movement

image sensor → A tiny camera chip that takes rapid pictures of the surface so changes in the image show the mouse movement

The mouse lights the surface under it with an LED or laser so the sensor can see the surface clearly → LED or laser light

Unlike older mice, an optical mouse has no moving ball inside it to track movement → no ball

An optical mouse tracks movement using a rolling ball under it → This describes an older ball mouse. An optical mouse has no ball and uses an LED or laser and an image sensor instead.

The scroll wheel and buttons on an optical mouse track the movement of the mouse → The buttons and scroll wheel send clicks and scrolling to the computer. The image sensor tracks the movement.

Section C: Definitions

optical mouse — An input device with an LED or laser under it that lights the surface while a sensor takes rapid images to track movement and move the pointer. It has no ball.

Section D: Fill in the Blanks

led ← ON

image ← CAPTURE(sensor)

dx ← newX - oldX

IF leftButton = PRESSED THEN
    SEND("click")
ENDIF

SEND(dx, dy) TO computer
MOVE(pointer, dx, dy)

Section E: Spot the Error

B — An optical mouse needs rapid images of the surface so it can see how the pattern changes as it moves. One image cannot show movement. It should say 'sensor takes rapid images'.

D — An optical mouse has no ball. It sends the movement (distance and direction) worked out from the images. It should say 'send movement to the computer'.

A — An optical mouse uses an LED or laser to light the surface. It does not use a rolling ball, which belongs to older mice. It should say 'LED shines light under mouse'.

B — Pressing a button makes the mouse send a click signal to the computer. If no signal were sent, nothing could be selected. It should say 'mouse sends a click signal'.

D — A scroll wheel signal makes the page move up or down. It does not change the pointer colour. It should say 'page moves up or down'.