Lesson 6 – Microscope and telescope Construct a ray diagram for a compound microscope with final image formed close to the near point of the eye (normal adjustment). Students should be familiar with the terms objective lens and eyepiece lens. Construct a ray diagram for an astronomical telescope with the final image at infinity (normal adjustment). State the equation relating angular magnification to the focal lengths of the lenses in an astronomical telescope in normal adjustment. Solve problems involving the compound microscope and the astronomical telescope (Problems can be solved either by scale ray diagrams or by calculation).

Compound microscope

Using a microscope – Making onion skin slides practical (Year 7!!!!) Eyepiece lens Objective lens

The object is placed at a distance just beyond the focal lens of the objective lens (so a short focal length is used)

A real inverted image is produced closer to the eyepiece lens than the focal length

The real image acts as an object for the eye piece lens The real image acts as an object for the eye piece lens. The eyepiece lens thus acts like a simple magnifying glass in the image formed by the objective

Enlarged image seen by eye. Largest when image at near point of eye.

Let’s make a microscope using two lens and then let’s draw our own ray diagram for a microscope

Astronomical telescope This is the 24 inch reflecting telescope at the Lowell Observatory in Flagstaff, Arizona, which was used to discover Pluto. Nearly all astronomical telescopes use mirrors rather than lenses, but we will learn how a telescope with lenses works.

Telescope – Ray diagram Angular magnification = fo/fe

Let’s make a telescope! Proud man