An object is placed at a distance of 20 cm from a concave lens of focal length 20 Find the image distance.
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What are similarities and differences between refraction, reflection, diffraction and absorption?

According to the image below, which season is about to begin in the southern hemisphere? a. summer b. autumn c. winter d. spring

The average atmospheric pressure on earth is approximated as a function of altitude by the relation patm = 101.325 (1 − 0.02256z)5.256, where patm is the atmospheric pressure in kpa, and z is the altitude in km with z = 0 at sea level. determine the approximate atmospheric pressures at atlanta (z = 306 m), denver (z = 1610 m), mexico city (z = 2309 m), and the top of mount everest (z = 8848 m).