PB15.0 Resolving power

PB15.0 Resolving power

By Tommy Xu

Let's review and get ready for today's class！😊​

​Interference

​Destructive

Constructive

· Full wavelength difference

Multiple Choice

WARM-UP QUESTION: The Contructive Interference has a ___ wavelength.

• 1

• 2

• $$\frac{1}{2}$$  

• Hahahah, I don't know, cuz I'm dumb enough.

Tommy​ Xu

​The interference and diffraction effects have consequences for the development of optical instruments. The diffraction produced by a single circular aperture consists of concentric light and dark bands. (see the graph on the right)

​

Multiple Choice

Diffraction changes with the _____ of the aperture.

• width

• size

• hight

• wavelength

If the aperture increases in size the width of the central maximum and the size of the diffraction pattern decrease.

​

Multiple Choice

If w increases then y _____.

• decreases

• increases

• stay constant

• I don't know again (no worries, shame on you 😊）

Resolving Power

Some text here about the topic of discussion

The resolving power of an instrument is the angular separation of the sources, which enables you to tell you are viewing two sources.

​What the textbook said:

Open Ended

What apparatus in real life can apply "resolving power"? Please give the name.

​Rayleigh Criterion

​

• ​θ is the angle subtended between the sources measured in seconds of arc​

• λ is thewavelength of the light used in metres​

• d is the diameter of the aperture in metres.

​The diffraction patterns merge as the objects are moved closer, making resolution poor.

Multiple Choice

This is __

• well resolved

• just resolved

• barely resolved

• not resolved

Multiple Choice

This is___

• well resolved

• not resolved

• just resolved

• I don't know

Multiple Choice

This is __

• just resolved

• well resolved

• no idea

• not resolved

Let's do some practices!

Easy right? Let's see 😊

What is the resolving power of the Hubble space telescope, which has an aperture of 1.8 m, when viewing two sources of red light of wavelength 650 nm?

​

​| Solution

​Find the resolving power of a microscope whose objective lens is 0.50 cm in diameter

​

(a) when blue light of 450 nm is used to illuminate the two sources;

​

(b) when red light of 650 nm is used to illuminate the two sources.

​

(c) Which colour of light would be best used to distinguish between two closely spaced specimens?

Thank u for ur attention! Bye bye

Tommy Xu