Assessment example Three
Parallax
MJH
PHASE 1
1a
Complete the following ray diagram for a convex lens and sketch a similar diagram for a concave lens.
4 marks
1b
4 marks
Read the value on the vernier scale
1c
4 marks
Identify the apparent image, real image, apparent depth and real depth.
1
Assessment example Three
Parallax
MJH
1d
4 marks
Place a dot (object) 12cm in
front of a plane mirror. Trace
two rays to locate the virtual
image in the mirror. Measure the
distance from the image to the
mirror.
PHASE 2
2a
8 marks
2
Assessment example Three
Parallax
MJH
8 marks
2b
Use the travelling microscope to measure the refractive index of the liquid.
Using the permanent marker make a mark on the inside of the dry beaker
3
Assessment example Three
Parallax
MJH
Using the microscope focus on the mark and take the reading call it reading A
Add 300 mls of the liquid supplied to the beaker.
Using the microscope focus on the image of the mark in the liquid call it reading B
Scatter some of the powder onto the surface of the liquid.
Focus the microscope on the surface and take the reading call it reading C
Write down the values for real depth, apparent depth
Calculate the refractive index of the liquid. RI = real / apparent
4
Assessment example Three
Parallax
MJH
8 marks
3a
Place the object (candle flame) 40 cm from the convex lens and find a sharp image on the screen.
Call this position A. Place a concave lens between the convex lens and the screen 12 cm from the
convex lens.
The image on the screen is now blurred. Move the screen further away from the lenses and find a
new sharp image on the screen. Call this position B
Measure the distance between
the two images.
The setup should look like this
picture.
5
Assessment example Three
3b
Parallax
MJH
Taking the distance from position A to the concave lens as the virtual object 4 marks
distance U and taking the distance from the concave lens to position B as the
real image distance calculate the focal length of the lens.
PHASE 4
4a
4 marks
Sketch a ray diagram showing how a virtual image
is formed in a convex lens acting in a magnifying glass.
4b
What do you understand by parallax error and how might you reduce it in taking readings
for the tasks completed
4c
4 marks
4 marks
Describe how you might demonstrate that the object distance in front of a plane mirror is
equal to the virtual image distance behind the mirror using parallax. You may test out
your method using the available apparatus.
6
Assessment example Three
Parallax
MJH
4d
8 marks
Use the data from the graph to
calculate the focal length of the
convex lens
[1/u + 1/v = 1/f ]
7