wave speed = frequency × wavelength What are the units?
P6.1 What are waves? Try these questions: 1.Bill counts 5 waves on a pond in 10 s. The distance between them is 80 cm. What is their speed? 5 waves in 10 s. Distance between is 80 cm. Speed? frequency = 5/10 = 0·5 Hz. speed = frequency × wavelength = 0·5 × 80 = 40 cm/s 2.Lizi reads the back label of her microwave oven. It says frequency = 2,450 MHz. The speed of microwaves is 3.00×10 8 m/s. What wavelength are they?microwave oven frequency = 2,450 MHz. speed = 3.00×10 8 m/s. speed = frequency × wavelength 3.00×10 8 = 2,450×10 6 × wavelength wavelength = 3.00×10 8 ÷ 2,450×10 6 = 0·122 m = 12·2 cm 3. Paul plays a note of wavelength 25 cm on his synthesiser. He knows the speed of sound is 340 m/s in air. What is its frequency? wavelength= 25 cm = 0·25 m. Speed = 340 m/s speed = frequency × wavelength 340 = frequency × 0·25 frequency = 340 ÷ 0·25 = 1,360 Hz
P6.1 What are waves? 1. The time required for the sound waves (v = 340 m/s) to travel from the tuning fork to point A is ____. 2. Two waves are traveling through the same container of nitrogen gas. Wave A has a wavelength of 1.5 m. Wave B has a wavelength of 4.5 m. The speed of wave B must be ________ the speed of wave A. a. 0.020 second b. 0.059 second c. 0.59 secondd. 2.9 second. a. one-ninthb. one-third c. the same as d. three times larger than
P6.1 What are waves? 3. TRUE or FALSE: Doubling the frequency of a wave source doubles the speed of the waves. 4. While hiking through a canyon, Noah Formula lets out a scream. An echo (reflection of the scream off a nearby canyon wall) is heard 0.82 seconds after the scream. The speed of the sound wave in air is 342 m/s. Calculate the distance from Noah to the nearby canyon wall. GIVEN: v = 342 m/s, t = 0.82 s (2-way) Find d (1-way) If it takes 0.82 s to travel to the canyon wall and back (a down-and-back time), then it takes 0.41 s to travel the one-way distance to the wall. Now use d = v t d = v t = (342 m/s) (0.41 s) = 140 m