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# Convert 2.3 µm into meters. PowerPoint PPT Presentation

Convert 2.3 µm into meters. 23000000 m 2300 m .0023 m .0000023 m. [Default] [MC Any] [MC All]. Optics. Units for this Unit. Nanometer (nm) = .000000001 m = 10 -9 m Angstrom (Å) = .0000000001 m = 10 -10 m. Diffraction Grating.

Convert 2.3 µm into meters.

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• 23000000 m

• 2300 m

• .0023 m

• .0000023 m

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Optics

### Units for this Unit

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

• Angstrom (Å) = .0000000001 m = 10-10 m

### Diffraction Grating

• 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.

### Diffraction Gratings

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

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

Constructive interference

Constructive interference

Destructive interference

Geometry

Path length difference

Constructive interference

Destructive interference

### Diffraction

d (sinq) = m l

d = grating spacing

q = angle of deviation

m = order of magnitude

l = wavelength

X

θ

θ

Y

d

θ

Path difference

= d sin θ

### Action of Diffraction Grating

• 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.

Turntable

Diffraction grating

Collimator C

θ

Light

source

Telescope T

Eyepiece

Achromatic lenses

Eye

Cross-wire

### Using a diffraction grating to measure the wavelength of light

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

### View through Diffraction Grating

• Diffraction grating placed in front of a methane air flame

• Spectrum of a star

• - Procyon

Monochromatic Light from a Helium-neon laser (λ =632.8 nm (10-9m)) shines on a diffraction grating that contains 150,500 lines/m. What is the grating separation?

• 6.328 x 10-7 m

• 1.58 106 m

• 1.505 x 105 m

• 6.64 x 10-6 m

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Monochromatic Light from a Helium-neon laser (λ =632.8 nm (10-9m)) shines on a diffraction grating that contains 150,500 lines/m). What is the angle of the first order maxima (m=1)?

• 3.2 degrees

• 5.5 degrees

• 6.7 degrees

• 8.5 degrees

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Monochromatic Light from a Helium-neon laser (λ =632.8 nm (10-9m)) shines on a diffraction grating that contains 150,500 lines/m). What is the angle of the second-order maxima (m=2)?

• 13.12 degrees

• 11.25 degrees

• 10.98 degrees

• 9.46 degrees

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• blue

• violet

• white

• red

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### As the slit distance in a diffraction grating get larger, what happens to the distance between maxima?

• The distance decreases

• The distance increases

• The distance stays the same

• The distance goes to zero

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Normal

### Law of Reflection

• Incoming and Reflected angles are equal

• Normal is perpendicular to surface at point of reflection

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

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

### Principle Rays

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

### Principle Rays

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.

Simple Camera

Virtual image

Real image

• real

• fake

• virtual

• imaginary

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### 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 areupright and reduced.

The De-Magnifier

F

2F

2F

F

F

2F

2F

F

### 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

2F

2F

F

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

image

### Convex Lens: Object Beyond 2F

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.

object

F

2F

2F

F

### 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.