Need Help! Thankyou

Question

. A lens has a focal length of 2m. A pencil is placed 3m from the lens.

1. Where will the image of the pencil be formed? (show all work) (3 marks)

1. Is the image inverted or upright? How do you know? (1 mark)

5. An object that is 45cm away from a lens has a magnification of 2.5.

1. What is the focal distance of this lens? (show all work) (3 marks)

1. Is the image created real or virtual and how do you know? (1 mark)

Answer 1

HI there,

You'll need to use the lens quation for these

1/s_o + 1/s_i = 1/f

Where s_o is the object distance and is + for real object to left of lens or - for virtual object to right of lens.

s_i is the image distance. It's positive for real images to right of lens.

f is the focal length which is + for converging or convex lens and - for diverging or concave lens.

The

The magnification equation M = y_i/y_o = -s_i/s_o will tell you if the image is inserted or not. M is negative for qn inverted image. y_i is the image height and is + for right side up image and y_o is the object height and is + for right side up object.

For example if you get M = -1.5 this indicates your image is inverted and larger.

As a rule of thumb, diverging lenses form virtual minified images. While converging lenses form inverted real images of real objects in front of a lens.

Hope this helps!