What does a grating do?
What will be an ideal response?
Grating is a piece of glass with thousands of microscopic parallel lines scribed onto its surface. Different wavelengths of light reflect from the grating at slightly different angles, so white light is spread into a spectrum and can be recorded, often by a charge-coupled device (CCD) camera. Recording the spectrum of a faint star or galaxy can require a long time exposure, so astronomers have developed multiobject spectrographs that can record the spectra of as many as 100 objects simultaneously. Multiobject spectrographs automated by computers have made large surveys of many thousands of stars or galaxies possible.
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For a system in mechanical equilibrium, the resultant
A) force must be zero. B) torque must be zero. C) both of these D) none of these
A rod of 2.0-m length and a square (2.0 mm × 2.0 mm) cross section is made of a material with a resistivity of 6.0 × 10^?8 ? / m. If a potential difference of 0.50 V is placed across the ends of the rod, at what rate is heat generated in the rod?
a. 3.0 W b. 5.3 W c. 8.3 W d. 1.3 W e. 17 W
A fish above the surface of water will see better in air if it has goggles that are
A) tinted blue. B) hemispherical. C) filled with water. D) extremely shiny. E) none of the above
Tan's face is 20 cm in front of a concave shaving mirror. If he observes his image to be twice as big and upright, what is the focal length of the mirror?
A) 10 cm B) -40 cm C) -50 cm D) 40 cm E) 50 cm