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Unformatted text preview: MidTerm IIa Name: Date: Phys224 Spring 2010 Dr. P. Hanlet Concept (3 points each) 1. A typical diverging lens has the shape: (a) concaveconcave (b) concaveconvex (c) flatconvex (d) convexconcave (e) convexconvex 2. A concave mirror with a radius of R =40 cm creates an image at infinity. The object was placed: (a) at infinity behind the mirror (b) at infinity in front of the mirror (c) 10 cm in front of the mirror (d) 20 cm in front of the mirror (e) 40 cm in front of the mirror 3. The intensity I of an electromagnetic wave (having electric field vector E =ˆ rE cos ( kx − ωt )) is proportional to: (a) E (b) √ E (c) E 2 (d) E 4 (e) 4 E 4. As a space traveller, your spacecraft breaks down while travelling at a constant velocity of 0 . 2 c relative to a nearby star. While outside repairing the vehicle you view another spacecraft approaching you at 0 . 3 c (in the same direction as your travel relative to the star), so you shine your laser pointer at it to catch the attention of the pilot. Relative to the pilot, at what speed, will the light from your laser pointer be moving? (a) 0 . 5 × 10 8 m/s (b) 3 . × 10 8 m/s (c) 0 . 1 × 10 8 m/s (d) 2 . 9 × 10 8 m/s (e) 2 . 5 × 10 8 m/s 5. Postitions of dark fringes are governed by which of the following equations? (a) d sin θ = mλ (b) n 1 sin θ 1 = n 2 sin θ 2 (c) Δ λ = h mc (1 − cos φ ) (d) all previous (e) none previous 1 Name: Date: Phys224 Spring 2010 Dr. P. Hanlet 6. The famous “twin paradox” describes twins which are separated when one travels on a high speed rocket to some distant place in the universe and back again. The paradox arises from: (a) the earthbound observer gets older (b) the spaceshipbound observer gets older (c) rocket ship leaves the earth for longer in the earth’s frame (d) rocket ship leaves the earth for longer in the ship’s frame (e) each twin gets older than his/her sibling 7. Similar to the example given in class, a train based observer in the S inertial reference frame watches a lightening bolt hit the front of the train at time t . Which equation would be used to compute the time of the event as seen by a ground based observer? (a) Δ t = γ parenleftbigg Δ t ′ + v Δ x ′ c 2 parenrightbigg (b) Δ t ′ = γ parenleftbigg Δ t − v Δ x c 2 parenrightbigg (c) t = γ parenleftbigg t ′ + vx ′ c 2 parenrightbigg (d) t ′ = γ parenleftBig t − vx c 2 parenrightBig (e) Δ t = γ Δ t 8. The figure below shows black body radiation spectra for three different temperatures. These spectra are important because they ushered in quantum mechanics since classical theory could not describe: 5000K 500K 273K (a) all spectra at small λ (b) the 273 K spectrum (c) the 500 K spectrum (d) the 5000 K spectrum (e) all spectra at large λ 9. In Compton’s wavelength shift equation, the angle refers to which direction?...
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 Spring '10
 Hanlet
 Special Relativity, Eγ, Dr. P. Hanlet

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