I already have the answers, but I need the explanation

Q1: A microwave oven works by producing standing waves of electromagnetic radiation inside a closed housing. Consider a microwave oven which is 30 cm wide and which has ve standing wave nodes 7 one at each end of the microwave plus three inside the oven itself. What does the frequency of the radiation need to be to produce this pattern? (6 points) A) 0.7 x 109 Hz B) 1.0x109Hz C) 1.5x109Hz D) 2.0x109Hz E) 4.0 x 109 Hz Q2: What is the intensity ratio ofa note of 60 dB compared with another note of 40 dB which has the same frequency? (6 points) A) 1.5 B) 15 C) 20 D) 100 E) 200 wQS: The near point of a farsighted person's uncorrected eyes is 80 cm. What power contact lens should be used to move the near point to 25 cm from this person's eyes? (6 points) A) 2.8 diopters B) -2.8 dioptcrs C) -4.0 diopters D) -4.2 diopters E) 4.2 diopters Q4: An object is placed in front of a lens which forms an image ofthe object. (6 points) A) If the lens is convex, the image cannot be virtual. B) If the image is real, then it is also inverted. C) Ifthe image is real, then it is also upright. D) Ifthe image is virtual, then it is also inverted. E) lfthe image is virtual, the lens must be a diverging lens. Q5: When light goes from one material into another material having a HIGHER index of refraction, (6 points) A) its speed, wavelength, and frequency all decrease. B) its speed and wavelength decrease, but its frequency stays the same. C) its speed decreases but its wavelength and frequency both increase. D) its speed decreases but its frequency and wavelength stay the same. E) its speed increases, its wavelength decreases, and its frequency stays the same