Physics Honors/AP 1 and 2

Homework

# Physics 25: 1-6 Optical Instruments

## Homework

Text Reading: Giancoli, Physics - Principles with Applications, Chapter 25: Sections 1 to 6

#### Study Points

• Section 1: Cameras focus light on a detector surface which may either be a film with a chemical coating that reacts to light, or a photosensitive electrical surface (charge-coupled device or CCD) that measure light wavelength and intensity. In digital cameras, these measurements are stored as codes for a given area of the picture (picture element or pixel).
• Section 2: The human eye focuses light through the cornea (primary area of focus) and the lens (fine adjustments). Failure to focus correctly can result in nearsightedness (objects focus in front of the retina, and far objects are out of focus), or farsightedness (objects focus behind the retina, and near objects are out of focus).
• Section 3: A magnifying glas uses a simple lens to enlarge the image reaching the human eye. Actual magnification must include the eye's location and focus.
• Section 4: Astronomical refracting telescopes use an eyepiece for fine focus and magnification adjustments, and a primary lens for magnification. Reflecting telescopes may incorporate a series of mirrors and lenses to increase focal length within a given physical telescope, or direct light to special detectors.
• Section 5: The compound microscope uses multiple lenses to drastically increase magnification of a near object.
• Section 6: Aberration is the deviation from a perfect focus. Spherical aberration occurs when non-parallel rays focus at different points, creating a circle of confusion or fuzzy image. Chromatic aberration occurs when light of different wavelengths focusses at different distances. Other forms of aberration are due to off-axis light striking different areas of the lens at different angles (coma, of-axis astigmatism).

### Key Equations

ConceptFormulaApplication
f-stop
Ratio of focal length to lens diameter
Indicates shutter speed required for exposure
Magnification at N (usually 25cm) Magnification perceived by single-lens magnifying glass for relaxed human eye
Telescope magnification Magnification achieved by Keplerian telescope.
Microscope magnification
Magnification achieved by compound microscope

### Web Lecture

Read the following weblecture before chat: Microscope and Telescope Optics

### Study Activity

Use the Zeiss interactive tutorial on Microsope characteristics to see how changing field lighting changes the microscope optics..

### Chat Preparation Activities

• Forum question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
• Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

### Chapter Quiz

• The chapter quiz is not yet due.

### Lab Work

If you want lab credit for this course, you must complete at least 12 labs (honors course) or 18 labs (AP students). One or more lab exercises are posted for each chapter as part of the homework assignment. We will be reviewing lab work at regular intervals, so do not get behind!