Work for Thursday, January 12, 2012 Day 2

1. Technologies and Applications of Optics – pages 482 – 492 a. Telescopes (page 482 and 488 – 489) i. Who invented the telescope? Describe this basic telescope. Hans Lippershey, this was a tube with lenses at either end. ii. Describe how telescopes have extended our knowledge and discovery of the solar system through time. Telescopes have extended our knowledge and discovery of the solar system by being able to view the moon in detail and observe mountains, discover four moons orbiting Jupiter as well as proving that the Sun was the centre of the solar system (rather than Earth). This also fueled a race to be able to build a better telescope and eventually to the use of mirrors being used in telescopes as they are much lighter than lenses. iii. What is a telescope? A telescope is an optical device that provides enlarged images of distant objects iv. Why is it difficult to see an object that is far away? There are two reasons. Firstly, any distant object appears very small. Secondly, the further away an object is, the dimmer it appears/becomes. v. Describe (with words and diagrams) how refracting and reflecting telescopes work and how they are different. Give an example of each type. Refracting telescopes have two lenses, one on each end of a long tube but the objective lens is a larger lens meaning that it has a very long focal length. It is useful for focussing light rays that are almost parallel when they hit the lens. In reflecting telescopes light enters from one end of a tube and reflects off a concave mirror towards a small, plane mirror. This mirror directs the light into an eyepiece, camera, or other instrument.

vi. Question #3, page 489 Some telescopes are very large because they are very heavy.

b. Cameras i. How have cameras (in cell phones specifically) had effects socially? Allows images to be taken and transported instantaneously around the world. Another affect is that because the image is digital, it allows for manipulation of the image. ii. How does the Canadian Food Inspection Agency use cameras? They are used to ensure quality control by monitoring food colour and comparing it with the colours of good quality food. iii. Copy figure 12.25 into your notes, define the highlighted terms, and describe how the camera works. Shutter – controls the length of time light is allowed in Diaphragm – controls the aperture Aperture – opening that the light passes through Cameras use convex lenses to refract light rays onto a light detector that record the image.

iv. Differentiate between a telephoto and a wide-angle lens A telephoto lens increases the amount of light that is collected and magnifies a distant object. A wide-angle lens captures a wider angle of the view because the lens is more spherical and has a shorter focal length. v. Question #4, page 486 A digital image is produced from pixels by numbers that represent each pixel. c. Microscopes i. Who (and when) made the first discovery that there were organisms smaller than could be seen with the unaided eye? Why was this discovery important (2 nd paragraph)? This discovery was made by Antonie van Leewenhoek in the 1600’s. This was important because prior to this, people did not recognize the importance of hand washing in terms of spreading germs ii. You already know “how to work” a microscope, now describe “how a microscope works” – stick with the compound microscope – like the ones we’ve used in class. A specimen is placed on a glass slide and illuminated. Light travels through the objective (convex lens) at the bottom of the tube close to the specimen. A second convex lens in the eyepiece further magnifies. Because the light rays cross over, the image is inverted. d. Lasers i. What is a laser? What is it used for (list LOTS of examples)? A laser is an optical device that produces a form of light in which all the light rays are almost perfectly parallel, and have the same wavelength, and all of the crests and troughts are lined up. It can be used for communications, consumer electronics, bar code readers, and DVD players. ii. Why do different colours of lasers appear brighter than others? Some colours appear brighter than others because our eyes are more sensitive to green light than red or blue. e. Photonics i. Describe another way of modelling how light travels. Light can also be described as tiny packets of energy called photons. In this model, the colour of light relates to the amount of energy carried by the photons. ii. Why is this second model of how light travels needed? Neither model (wave or photons) accounts for all, but the theories together can account for all properties of light. iii. What are photonics? Photonics is a technology that makes use of the way in which light travels as photons. 2. Human Vision Handout – pages 468 – 477 --- complete questions and label diagrams. 3. IF you get all this done before the end of class, read pages 468 – 477. This is NOT for homework.