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# Light Optical instruments

## Virtual vs Real Images

### The light rays form a real image at the focus.

Physics StackExchange Virtual vs Real image

## Digital cameras in smartphones

### All things being equal, cell phone cameras should do a terrible job. Yet in recent years, engineers, mathematicians and coders have made amazing progress in allowing these tiny cameras to take some amazing photographs. They use mathematical and computer science techniques to analyse the data, and create a photo far better than one might otherwise expect. This article explains how.

Applied math: The future of photography on phones depends on coding

## Magnifying Glass

### It allows us to focus on objects closer than the near point, so that they make a larger, and therefore clearer, image on the retina.

From Home-Science.com

When the arrow is moved to a particular distance behind the glass, it looks like it reversed itself. When light passes from one material to another, it can bend or refract.

Here, light traveled from the air, through the glass, through the water, through the back of the glass, and then back through the air, before hitting the arrow.

Anytime that light passes from one medium, or material, into another, it refracts.

Just because light bends when it travels through different materials, doesn’t explain why the arrow reverses itself.

To explain this, you must think about the glass of water as if it is a magnifying glass. When light goes through a magnifying glass the light bends toward the center. Where the light all comes together is called the focal point, but beyond the focal point the image appears to reverse because the light rays that were bent pass each other and the light that was on the right side is now on the left and the left on the right, which makes the arrow appear to be reversed.

lenses

## MCAS example problems

MCAS light and optics practice problems

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### AP Physics: optical instruments PDF file

25.1: Cameras: Film and Digital
25.2: The Human Eye; Corrective Lenses
25.3: Magnifying Glass
25.4: Telescopes
25.5: Compound Microscope
25.6: Aberrations of Lenses and Mirrors
25.7: Limits of Resolution; Circular Apertures
25.8: Resolution of Telescopes and Microscopes; the λ Limit
25.9: Resolution of the Human Eye and Useful Magnification
25.10: Specialty Microscopes and Contrast
25.11: X-Rays and X-Ray Diffraction
25.12: X-Ray Imaging and Computed Tomography (CT Scan)

## Learning Standards

2016 Massachusetts Science and Technology/Engineering Curriculum Framework

HS-PS4-1. Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling within various media. Recognize that electromagnetic waves can travel through empty space (without a medium) as compared to mechanical waves that require a medium

HS-PS4-3. Evaluate the claims, evidence, and reasoning behind the idea that electromagnetic radiation can be described by either a wave model or a particle model, and that for some situations involving resonance, interference, diffraction, refraction, or the photoelectric effect, one model is more useful than the other.

HS-PS4-5. Communicate technical information about how some technological devices use the principles of wave behavior and wave interactions with matter to transmit and capture information and energy. Emphasis is on qualitative information and descriptions. Examples of principles of wave behavior include resonance, photoelectric effect, and constructive and destructive interference.

SAT subject test in Physics: Waves and optics

• General wave properties, such as wave speed, frequency, wavelength, superposition, standing wave diffraction, and Doppler effect
• Reflection and refraction, such as Snell’s law and changes in wavelength and speed
• Ray optics, such as image formation using pinholes, mirrors, and lenses
• Physical optics, such as single-slit diffraction, double-slit interference, polarization, and color

A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas (2012)

PS4.A: WAVE PROPERTIES

When a wave passes an object that is small compared with its wavelength, the wave is not much affected; for this reason, some things are too small to see with visible light, which is a wave phenomenon with a limited range of wavelengths corresponding to each color. When a wave meets the surface between two different materials or conditions (e.g., air to water), part of the wave is reflected at that surface and another part continues on, but at a different speed. The change of speed of the wave when passing from one medium to another can cause the wave to change direction or refract. These wave properties are used in many applications (e.g., lenses, seismic probing of Earth)… the wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing. The reflection, refraction, and transmission of waves at an interface between two media can be modeled on the basis of these properties… At the surface between two media, like any wave, light can be reflected, refracted (its path bent), or absorbed. What occurs depends on properties of the surface and the wavelength of the light…. Lenses can be used to make eyeglasses, telescopes, or microscopes in order to extend what can be seen. The design of such instruments is based on understanding how the path of light bends at the surface of a lens.