11 (1 point) Noise from a construction site can be heard at a distance of 21.0 km. Assuming that the sound is emitted equally in all directions and that the threshold of audibility is 1.0 x 10-12 W/m7, find the emitted sound power of the construction site. Give the answer in mW Q12: Question 12 (1 point) A completely black metal sphere of radius 15.0cm is heated to 211C What is the total power of the electromagnetic waves emitted by the sphere? Question 13 (1 point) Light of wavelength 420 m passes through a double slit. The interference pattern is observed on a screen located at 6.30 m from the slits. The bright bangs are spaced at 9.00 mm. What is the separation of the two slits? Give the answer in mm. Question 14 (1 point) In the construction of buildings in an earthquake region, what relationship should be achieved between the natural oscillation frequency of the building and the typical earthquake frequencies? 1-The frequency of the building must be almost the same as the seismic frequencies but slightly lower. 2-The frequency of the building must be very different from the seismic frequencies. 3- The frequency of the building must be exactly equal to the seismic frequencies. 4- The frequency of the building should be almost the same as the seismic frequencies but slightly higher but slightly higher than the seismic frequencies Question 18 (1 point) An electric current heats a tungsten wire to a temperature of 3200 K. Assuming that the wire behaves as a perfect emitter at this temperature, calculate the wavelength of the emission peak. Give the answer in nm. Question 19 (1 point) Monochromatic light is incident on a diffraction grating of length 80.0 mm and comprising 47,000 lines. The second order maximum is observed at an angle of 38.4. What is the wavelength of the incident light? Give the answer in nm. Question 21 (1 point) A radio telescope of diameter 340 m is used to detect sources emitting waves of length 20.0 cm. What is the minimum angular separation between two different sources that this system could resolve? Give the answer in degrees Question 23 (1 point) A measurement of the speed of an electron gives 1.20 x 106 m/s with an uncertainty of 7%. What is the minimum uncertainty of its position? Give the answer in nm. Question 24 (1 point) A pipe with an open end and a closed end produces a fundamental frequency of 100 Hz. How long is it? (The speed of sound in air is 340 m/s