Seat: PHYS 1510 (Spring 2013) Exam #1, V1 Multiple choice (4 pts each) circle the correct answers.

Transcription

1 Seat: PHYS 1510 (Spring 2013) Exam #1, V1 Name: Multiple choice (4 pts each) circle the correct answers. 1. You use a converging lens to make a focused image on a viewing screen. A piece of cardboard is lowered just in front of the lens to cover the top half of the the lens. What happens to the image on the screen? (a) The upper half of the image will vanish. (b) The lower half of the image will vanish. (c) The image will become fuzzy and out of focus. (d) The image will become dimmer. (e) Nothing 2. A sinusoidal wave traveling on a string with a tension of 16 N has a period of 0.25 s, a wavelength of 40 cm, and an amplitude of 8 cm. The speed of the wave is (a) 10 cm/s (b) 160 cm/s (c) 2 cm/s (d) 32 cm/s (e) 1 cm/s (f) 16 cm/s 3. Two guitar strings made of the same type of wire have the same length. String 1 has a higher pitch than string 2. Circle all of the correct statements. (a) The wave speed of string 1 is greater than that of string 2. (b) The tension in string 2 is greater than that in string 1. (c) The wavelength of the lowest standing-wave mode on string 2 is longer than that on string 1. (d) The wavelength of the lowest standing-wave mode on string 1 is longer than that on string Yellow light of wavelength 590 nm passes through a 10-µm-wide slit and is viewed on a screen 2.0 m behind the slit. If the width of the slit is narrowed, the band of light on the screen will (a) become narrower. (b) become wider. (c) stay about the same. 5. The distance between the objective and eyepiece of a telescope is 55 cm. The focal length of the eyepiece is 5 cm. What is the focal length of the objective? (a) 11 cm (b) 25 cm (c) -25 cm (d) 60 cm (e) none of the above. 6. Light from a flower goes through the lens of your eye and an image of the flower is formed on the back of your eye. The image is (a) upright. (b) flipped. (c) upright or flipped depending on how close the flower is to your eye.

2 Problems: Show all work to receive full credit. In all problems choose the positive x-direction to be to the right and the positive y-direction to be up. 6 pts 1. The planet Neptune is m from the earth. Its diameter is m. What diameter telescope objective would be necessary to just barely see Neptune as a disk rather than as a point of light? Assume a wavelength of 550 nm pts A slide projector creates a 90.0 cm high image of a 2.0 cm tall slide. The screen is 300 cm from the lens. (a) How far is the slide from the lens? (b) What is the focal length of the lens?

3 6 pts 3. Two loudspeakers emit sound waves along the x-axis. The sound has a maximum intensity when the speakers are 24 cm apart. The sound intensity decreases as the distance between the speakers is increased, reaching zero at a separation of 30 cm. (a) What is the wavelength of the sound? (b) If the distance between the speakers continues to increase, at what separation will the intensity next again be a maximum? 4. 6 pts Ginger (mass 60 kg) uses a 3.5-m-long rope to pull Sandra (mass 70 kg) across the floor at a constant speed of 1.3 m/s. The rope has a mass of 120 g. Sandra signals to Ginger by plucking the rope, sending a wave pulse. The pulse reaches Ginger 200 ms later. What is the tension in the rope?

4 12 pts 5. The figure shows the interference pattern on a screen 1.10 m behind a diffraction grating. The light has a wavelength of 600 nm. There are two lengths, L a and L b, marked on the figure with L a = 41.1 cm and L b = 66.7 cm. (a) How many lines per millimeter does the grating have? (b) Is L b correct given the information and the value L a? Show work to get credit.

5 Equations Basic Mathematic Formulas sin θ = O/H cos θ = A/H tan θ = O/A H 2 = O 2 + A 2 A circ = πr 2 C circ = 2πr V sph = 4π 3 r3 A sur of sph = 4πr 2 x = b ± b 2 4ac 2a F net = F 1 + F = m a τ = rf = r F = rf sin ϕ F = mv 2 /r m p = kg m e = kg 1 u = kg m α = 4u index of refraction: Water (1.33), Ethyl Alc. (1.36), Glass (1.50), Diamond (2.42) ( [ x y(x, t) = A cos 2π λ ± t ]) T Chapter 15 T = 1/f v = fλ v str = T s /µ v snd = 343 m/s c = m/s I = P/A I = P src /(4πr 2 ) f = f 0 /(1±[v s /v]) f ± = (1±[v o /v])f 0 Chapter 16 λ m = 2L/m f m = m(v/[2l]) m = 1, 2, 3... Chapter 17 w = 2λL/a a sin θ p = pλ y p = L tan θ p p = 1, 2, 3... d sin θ m = mλ d sin θ m = (m + 1/2)λ y m = L tan θ m m = 0, 1, 2... Chapter 18 θ r = θ i n 1 sin θ 1 = n 2 sin θ 2 θ c = sin 1 (n 2 /n 1 ) v = c n 1 s + 1 s = 1 f m = s s Chapter 19 d min = 0.61λ/NA θ 1 = 1.22λ/D P = 1/f M = θ/θ 0 = 25 cm/f M = f o /f e M = L 25 cm/(f o f e ) Chapter 20 F 1 on 2 = K q 1 q 2 /r 2 K = N m 2 /C 2 e = C E = Fon q /q E tot = E 1 + E E = K q /r 2 E = Q/(ε 0 A) ε 0 = C 2 /(N m 2 ) Chapter 21 U elec = qv K f + qv f = K i + qv i V = Kq/r V C = Q/C C = κε 0 A/d U C = 1 2 C( V c) 2 u E = 1 2 κε 0E 2 V = x d V c E = V C d 1 ev = J

6 Chapter 22 I = q/ t R = ρl/a I = V/R P emf = IE P R = I V R = I 2 R = ( V R ) 2 /R V i = 0 i Chapter 23 Iin = I out R eq = R 1 +R (1/C eq ) = (1/C 1 )+(1/C 2 )+... (1/R eq ) = (1/R 1 ) + (1/R 2 ) +... C eq = C 1 + C Chapter 24 F = qvb sin α F = ILB τ = (IA)B sin θ r = mv/( q B) B = µ 0 I/(2πr) B = µ 0 I/(2R) B = µ 0 IN/L µ 0 = T m/a Chapter 25 Φ = AB cos θ E = Φ/ t E 0 = cb 0 E = hf I = I 0 cos 2 θ λ peak = nm K/T β = v/c Chapter 27 t = τ/ 1 β 2 L = 1 β 2 l p = γmu γ = 1/ 1 u 2 /c 2 E = γmc 2 = mc 2 +(γ 1)mc 2 u = (u v)/(1 uv/c 2 ) u = (u +v)/(1+u v/c 2 ) Chapter 28 h = J s λ = h/(mv) x p x h/(2π) V stop = K max /e = (hf E 0 )/e 2d cos θ = mλ m = 1, 2, 3,... Chapter 29 E phot = E atom = E f E i 2πr = nλ E n = 13.6 ev/n 2 r n = n 2 a B a B = nm λ n m = 91.1 nm/(1/m 2 1/n 2 ) m = 1, 2, 3... n = m + 1, m + 2, m h = h/(2π) L = l(l + 1) h l = 0, 1, 2... m = l, l+1, , l 1, l m s = ±1/2 A = Z + N Chapter 30 B = (Zm H + Nm n m atom ) MeV/u A ZX A 4 Z 2 Y + α + E A ZX A Z+1 Y +β+e N = N 0 e t/τ N = N 0 (1/2) t/t 1/2 t 1/2 = τ ln 2 R = N/τ dose equiv (Sv) = dose(gy) RBE