A. 23000000 mB. 2300 mC. .0023 mD. .0000023 m

[Default][MC Any][MC All]

• Nanometer (nm) = .000000001 m = 10-9 m

• Angstrom (Å) = .0000000001 m = 10-

10 m

• A large number of equally spaced parallel slits is called a diffraction grating.

• A diffraction grating can be thought of as an optical component that has tiny grooves cut into it. The grooves are cut so small that their measurements approach the wave length of light.

• A diffraction grating splits a plane wave into a number of subsidiary waves which can be brought together to form an interference pattern.

Constructive interference Constructive interference Destructive interference

If you now send the light from the two openings onto a screen, an interference pattern appears, due to differing path lengths from each source

• we have constructive interference if paths differ by any number of full wavelengths

• destructive interference if difference is half a wavelength longer or shorter

Geometry Path length difference

Constructive interference

Destructive interference

d (sin) = m

d = grating spacing = angle of deviationm = order of

magnitude = wavelength

• If d is the slit spacing then the path difference between the light rays X and Y = d sin θ.

• For principal maxima, d sin θ = mλ.• The closer the slits, the

more widely spaced are the diffracted beams.

• The longer the wavelength of light used, the more widely spaced are the diffracted beams.

d

Path difference= d sin θ

θ

θ

θ

X

Y

• A spectrometer is a device to measure wavelengths of light accurately using diffraction grating to separate.

Lightsource

Collimator C

Achromatic lenses

Diffraction grating

Telescope T

Eyepiece

Eye

θ

Cross-wire

Turntable

• Diffraction grating placed in front of a methane air flame

Spectrum of a star - Procyon

A. 6.328 x 10-7 mB. 1.58 106 mC. 1.505 x 105 mD. 6.64 x 10-6 m

A. 3.2 degreesB. 5.5 degreesC. 6.7 degreesD. 8.5 degrees

A. 13.12 degreesB. 11.25 degreesC. 10.98 degreesD. 9.46 degrees

A. blueB. violet C. whiteD. red

A. The distance decreasesB. The distance increasesC. The distance stays the sameD. The distance goes to zero

Law of Reflection

• Incoming and Reflected angles are equal• Normal is perpendicular to surface at point of

reflection

Normal

Mirrors• Planar

• “flat” mirrors

• Spherical• Concave

• Convex

Some Terminology

• Center of Curvature (C)

• Principle Axis

• Focal Point (F)F

Ray Diagrams• Image location can be predicted with ray diagrams• All you need to do is draw the three Principle Rays to

determine the location, orientation, and size of the image.

Draw this!!!!

Principle Rays

1. Draw a ray coming from the top of the object, parallel to the axis. It reflects through the focal point.

Principle Rays

2. Incident ray is through focal point, reflects parallel to axis.

Principle Rays

3. Incident ray is through center of curvature, reflects straight back.

Ray Diagram• See where the 3 rays converge? That’s the location of the image.• For this situation, the image is smaller and inverted.

Ray Diagrams

• Image location can be predicted with ray diagrams• Image may appear in front of the mirror – real image

• Real images can be seen reflected onto a sheet of paper.

• Image may appear behind the mirror – virtual image• Virtual images cannot be seen reflected onto a sheet of paper.

Real vs. Virtual Images• The virtual image in a plane mirror will appear as far

from the mirror as the object, so if you stand 2 m in front of the mirror, your reflection appears to be 4m away from you.

Virtual image

Real image

Simple Camera

A penguin looks into a planar (flat) mirror and sees his image on the other side of the mirror. What type of image is formed?

A. realB. fakeC. virtualD. imaginary

Convex Lenses

Thicker in the center than edges. • Lens that converges

(brings together) light rays.

• Forms real images and virtual images depending on position of the object

The Magnifier

Concave Lenses

• Lenses that are thicker at the edges and thinner in the center. • Diverges light rays • All images are

upright and reduced.The De-Magnifier

Convex Lenses

Rays traveling parallel to the principal axis of a convex lens will refract toward the focus.

Rays traveling directly through the center of a convex lens will leave the lens traveling in the exact same direction.

•• • •F F 2F2F

•• • •F F 2F2F

Rays traveling from the focus will refract parallel to the principal axis.

•• • •F F 2F2F

Convex Lens: Object Beyond 2F

•• • •F F 2F2F

object

image

The image formed when an object is placed beyond 2F is located behind the lens between F and 2F. It is a real, inverted image which is smaller than the object itself.

Optics Problems

Equations:*

* Refer to your Optics Reference Sheet

An object stands a distance of 36 cm from a concave mirror. An image forms 18 cm from the mirror.

What is the focal length of the mirror?

An object stands a distance of 36 cm from a concave mirror. An image forms 18 cm from the mirror.

What is the center length of the circle?

An object stands a distance of 36 cm from a concave mirror. An image forms 18 cm from the mirror.

What is the magnification factor of the image?

An object stands a distance of 36 cm from a concave mirror. An image forms 18 cm from the mirror.

If the object has a height of 5 cm, what is the height of the image?

An object stands a distance of 36 cm from a concave mirror. An image forms 18 cm from the mirror.

State the relative size (bigger/smaller), orientation (upright/inverted), and type (real/virtual) for the image that is produced.