Telescopes and the Electromagnetic Spectrum Section 3 Optical

Telescopes and the Electromagnetic Spectrum Section 3

Optical Astronomy • Optical telescope – Collects visible light for closer observation – 2 lenses • Objective lens: collects light and forms an image at the back of the telescope • Eyepiece: magnifies the images from the objective lens

• Without an optical telescope you can see about 6, 000 stars • With an optical telescope you can see millions of stars

Refracting Telescopes • Use a set of lenses • Curved objective lens bends light and focuses it to the eyepiece • Eyepiece lens magnifies the image • Disadvantage: if the curved lens is too large the glass will sag and distort the image

Reflecting Telescopes • • Use curved mirrors Large curved mirror reflects light to a focal point The focal point reflects light to the eyepiece Advantages: 1. Mirrors can be made very large 2. Mirrors are polished on one side to prevent flaws from glass 3. Mirrors reflect light of all colors to the same place

• What do you think would be an advantage to having a telescope in space compared to one on the ground?

Electromagnetic Spectrum • Made of all the wavelengths of electromagnetic radiation • Visible light is only a small portion • Earth’s atmosphere allows these in…. – Infrared, visible light, some ultraviolet, and radio • Earth’s atmosphere blocks…. – Gamma, X rays, some ultraviolet • Astronomers can detect…. – Visible light, infrared, and radio waves