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# MCQ in Physics Part 7 | ECE Board Exam

This is the Multiples Choice Questions Part 7 of the Series in Physics as one of the General Engineering and Applied Sciences (GEAS) topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including past Board Questions in General Engineering and Applied Sciences (GEAS), Physics Books, Journals and other Physics References.

#### Continue Practice Exam Test Questions Part 7 of the Series

Choose the letter of the best answer in each questions.

301. The wavelength of a source wave in a certain material as measured is 18 cm. The frequency of the wave is 1900 Hz. Compute the speed of sound wave?

A. 342 m/s

B. 400 m/s

C. 542 m/s

D. 300 m/s

Explanation:

302. A horizontal cord 5 m long has a mass of 2.5 grams. What must be the tension in the cord if the wavelength of a 120 Hz wave on it is to be 50 cm?

A. 1.50 N

B. 1.80 N

C. 2.50 N

D. 4.30 N

Explanation:

303. A 3-m string is driven by a 240 Hz vibrator at its end. Determine the speed of transverse waves on the string if it resonates four segments?

A. 340 m/s

B. 360 m/s

C. 430 m/s

D. 420 m/s

Explanation:

304. A guitar string 30 cm long resonates in its fundamental to a frequency of 250 Hz. What is the tension in the string if 80 cm of the string โweighsโ 0.80 grams?

A. 20 N

B. 30 N

C. 10 N

D. 40 N

Explanation:

305. A piano string with a length of 1.17 m and a mass of 21.0 g in under tension of 6.4 x 103 N, what is the fundamental frequency?

A. 225 Hz

B. 187 Hz

C. 255 Hz

D. 290 Hz

Explanation:

306. A rope 4 ft. long weighs 0.7 lb. A blow on the rope produces a transverse wave. Determine the velocity of the wave considering that the tension is 40 lb.

A. 75.8 ft/s

B. 95.7 ft/s

C. 78.5 ft/s

D. 85.8 ft/s

Explanation:

307. What is the relative intensity level of sound in decibels it its intensity is 3 x 10-7 W/cm2?

A. 94.8

B. 78.7

C. 80.5

D. 75.4

Explanation:

308. A wave has pressure amplitude of 5 dynes/cm2 and a velocity of 35.7 m/s, what is the absolute intensity considering that 0.001293 gm/cm?

A. 1.27 x 10^-8 W/cm2

B. 1.47 x 10^-8 W/cm2

C. 3.27 x 10^-8 W/cm2

D. 2.71 x 10^-8 W/cm2

Explanation:

309. A train blowing its whistle at 750 Hz approaches a station at the rate of 35 mph. What frequency is heard by a man standing at the station considering the velocity of sound in air 1100 ft/s?

A. 739.7 Hz

B. 857.4 Hz

C. 716.4 Hz

D. 786.7 Hz

Explanation:

310. Two cars A and B are traveling toward each other at speeds of 45 km/hr and 70 km/hr respectively. If A blowing its horn, what is the relative pitch heard by a passenger in B, considering that the velocity of sound is 344 m/s

A. 1.043

B. 1.021

C. 1.096

D. 1.078

Explanation:

311. An explosion occurs at a distance of 5 km from the observer. How long after the explosion does a person hear if the temperature is 18ยฐC? Note: the speed of sound at STP (standard temperature and pressure) is 332 m/s and changes by 0.6 m/s for every 1 ยฐC change in temperature.

A. 14.58 s

B. 12.45 s

C. 11.87 s

D. 17.54 s

Explanation:

312. What is the speed of sound in neon gas at temperature of 25ยฐC considering that the molecular mass if this gas is 20.18 kg/mol? Neon is monoatomic. Use k = 1.67

A. 543.7 m/s

B. 478.6 m/s

C. 321.7 m/s

D. 447.5 m/s

Explanation:

313. What is the wavelength of yellow light whose frequency is 5 x 1014 Hz?

A. 800 mm

B. 200 mm

C. 600 mm

D. 700 mm

Explanation:

314. What is the angle of refraction of light as a beam of parallel light enters a block of ice at angle of incidence of 30ยฐ? The index of refraction of ice is 1.31 and that of air is 1.0.

A. 45ยฐ

B. 30ยฐ

C. 22ยฐ

D. 26ยฐ

Explanation:

315. A light ray is incident at an angle of 45ยฐ on one side of a glass plate of index of refraction 1.6. Find the angle at which the ray emerges from the other side of the plate.

A. 26ยฐ

B. 20ยฐ

C. 22ยฐ

D. 28ยฐ

Explanation:

316. It was found out that the speed of light in water is 75% of its speed in vacuum. What is the index of refraction of water?

A. 1.46

B. 1.33

C. 1.26

D. 1.67

Explanation:

317. A glass plate is 0.6 cm thick and has a refractive index of 1.55. Compute how long will it take for a pulse of light to pass through the plate?

A. 4.41 x 10-12 s

B. 3.11 x 10-11 s

C. 1.34 x 10-12 s

D. 2.34 x 10-11 s

Explanation:

318. A light passes from glass to water. If the index of refraction for glass is 1.54 and for water is 1.33, compute the critical angle for this light to pass the glass.

A. 59.7ยฐ

B. 45.8ยฐ

C. 67.4ยฐ

D. 50.9ยฐ

Explanation:

319. A light source emits a total luminous flux of 1000 lumens and distributed uniformly over 25% of a sphere. What is the luminous intensity at 2.5-meter distance?

A. 413 cd

B. 243 cd

C. 134 cd

D. 318 cd

Explanation:

320. A light bulb emits a total luminous flux of 1700 lumens, distributed uniformly over a hemisphere. What is the illuminance at a distance of 2 meters?

A. 67.65 lm/m2

B. 35.70 lm/m2

C. 59.87 lm/m2

D. 23.56 lm/m2

Explanation:

321. A light bulb is used to light a bunker 10 ft. below. A chair sits on the floor of the bunker 3 feet from a spot directly below the bulb. What is the illumination on the floor around the chair if the luminous intensity is 150 candles?

A. 2.38 footcandles

B. 2.43 footcandles

C. 3.87 footcandles

D. 1.38 footcandles

Explanation:

322. A light ray passing through air and strikes a glass surface at an angle of 55ยฐ from the normal surface. What is the angle between the reflected light and the surface?

A. 55ยฐ

B. 25ยฐ

C. 35ยฐ

D. 45ยฐ

Explanation:

323. A converging lens of focal length 20 cm is placed 37 cm in front of a screen. At what distance that the object be placed so that its image appears on the screen?

A. 43.5 cm

B. 35.7 cm

C. 27.6 cm

D. 50.7 cm

Explanation:

324. In what positions will a converging lens of focal length 10 cm from an image of luminous object on a screen located 50 cm from the object?

A. 11.52 cm and 38.48 cm from the object

B. 10 cm and 40 cm from the object

C. 13.82 cm and 36.18 cm from the object

D. 12.56 cm and 37.44 cm from the object

Explanation:

325. A lens has a convex surface of radius 17 cm and a concave surface of radius 38 cm and is made of glass of refractive index 1.55. Calculate the focal length of the lens and classify the type of lens whether diverging or converging?

A. 55.93 cm converging lens

B. 57.45 cm diverging lens

C. 55.93 cm diverging lens

D. 57.45 cm converging lens

Explanation:

326. A double convex lens has faces of radii 16 and 18 cm. When an object is 20 cm from the lens, a real image is formed 30 cm from the lens. What is the focal length of the lens?

A. 11 cm

B. 10 cm

C. 12 cm

D. 14 cm

Explanation:

327. A double convex lens has faces of radii 22 and 24 cm. When an object is 30 cm from the lens, a real image is formed 45 cm from the lens. Compute the refractive index of the lens material

A. 1.64

B. 1.32

C. 1.21

D. 1.76

Explanation:

328. A 50 watt incandescent lamp has a mean spherical luminous intensity of 66.5 candelas. Compute the total luminous flux radiated by the lamp?

A. 842 lm

B. 457 lm

C. 786 lm

D. 987 lm

Explanation:

329. A 250 W light source has a mean spherical luminous intensity of 87.5 candelas. Compute the luminous intensity of the lamp?

A. 4.7 lm/s

B. 4.4 lm/s

C. 2.0 lm/s

D. 1.7 lm/s

Explanation:

330. Compute the illumination on a surface 5 ft distance from a 100-cd source if the surface makes an angle of 18ยฐ with the rays?

A. 1.67 lm/ft2

B. 1.50 lm/ft2

C. 1.24 lm/ft2

D. 2.13 lm/ft2

Explanation:

331. Estimate the distance for which a 30-cd lamp provide the same illumination as a standard lamp of 80-cd placed 17 ft from the screen?

A. 9.76 ft

B. 8.5 ft

C. 12.7 ft

D. 10.41 ft

Explanation:

332. A Plano-convex lens has a focal length of 35 cm and an index of refraction 1.53. Find the radius of the convex surface.

A. 18.55 cm

B. 15.78 cm

C. 20.78 cm

D. 17.55 cm

Explanation:

333. If a beam of polarized light has one-twelfth of its initial intensity after passing through an analyzer, what is the angle between the axis of the analyzer and the initial amplitude of the beam?

A. 65.73ยฐ

B. 76.27ยฐ

C. 73.22ยฐ

D. 67.54ยฐ

Explanation:

334. An observer sees a spaceship, measured 100 m long when at rest. He passed by in uniform motion with the speed of 0.5 c. While the observer is watching the spaceship, a time of 2 s elapses on a clock on board the ship, what is the length of the moving spaceship?

A. 82 m

B. 85 m

C. 83 m

D. 87 m

Explanation:

335. The captain of a spacecraft send a pulse of light towards earth and then exactly 1 min. later (as measured by the clock on the spacecraft), sends a second pulse. An observer on earth sees the second pulse arrive 4 minutes after the first. What is the velocity of the spacecraft relative to the earth?

A. 0.987c

B. 0.968c

C. 0.954c

D. 0.953c

Explanation:

336. What is the rest energy of electron equivalent to its rest mass? 1Mev = 1.60 x 10^-13 J and mass of electron is 9.11 x 10^-31 kg.

A. 0.512 MeV

B. 0.987 MeV

C. 0.345 MeV

D. 0.675 MeV

Explanation:

337. What is the frequency of photon having energy of 2 eV?

A. 560 THz

B. 300 THz

C. 250 THz

D. 480 THz

Explanation:

338. A red light passes an empty space. What is the momentum of a single photon of red light whose frequency is 400 x 1012 HZ?

A. 8.8 x 10-28 kg m/s

B. 7.6 x 10-28 kg m/s

C. 5.4 x 10-28 kg m/s

D. 6.5 x 10-28 kg m/s

Explanation:

339. The eye can detect as little as 1 x 10^-18 J of electromagnetic energy. How many photons of orange light whose wavelength is 600 nm present in the energy?

A. 5

B. 4

C. 3

D. 1

Explanation:

340. What is the speed of sound through compressed water (100 kPa) if its volume decreased by 0.005% of its original volume?

A. 1414 m/s

B. 1250 m/s

C. 1130 m/s

D. 1200 m/s

Explanation:

341. What is the bulk modulus of steel if the sound waves traveled at approximately 5900 m/s? Note: the density of steel is 7900 kg/m3

A. 2.75 x 1011 Pa

B. 1.25 x 1011 Pa

C. 1.15 x 1011 Pa

D. 2.45 x 1011 Pa

Explanation:

342. A certain loud speaker has a circular opening with a diameter of 15 cm. Assume that the sound it emits is uniform and outward through this entire opening. How much power is being radiated by the loudspeaker if the sound intensity at opening is 150 ยตW/m2?

A. 1.77 ยตW

B. 1.87 ยตW

C. 2.65 ยตW

D. 3.41 ยตW

Explanation:

343. Sound intensity that reaches 1.2 W/m2 is painful to human ear. How many decibels is 1.2 W/m2?

A. 240.5 dB

B. 170.4 dB

C. 120.8 dB

D. 134.5 dB

Explanation:

344. Compute the ratio of the intensities of sounds if one is 12 times louder than the other?

A. 13.47 dB

B. 15.85 dB

C. 18.76 dB

D. 14.54 dB

Explanation:

345. An automobile moving at 30 m/s is approaching a building whistle with a frequency of 500 Hz. If the speed of sound in air is 340 m/s what is the apparent frequency of the whistle heard by the driver?

A. 459 Hz

B. 458 Hz

C. 457 Hz

D. 456 Hz

Explanation:

346. What is the mass of electron traveling at half the speed of light?

A. 1.05 x 10-30 kg

B. 2.31 x 10-30 kg

C. 1.56 x 10-31 kg

D. 1.61 x 10-31 kg

Explanation:

347. A medium unshaded lamp hangs 8 m directly above the table. To what distance should it be lowered to increase the illumination to 4.45 times its former value?

A. 4.02 m

B. 3.86 m

C. 3.79 m

D. 4.21 m

Explanation:

348. A floodlight emitting 25,000 candelas in the center of its beam is aimed at 50ยฐ to a point on the ground 20 meters away. The illumination of the point in flux is:

A. 54.12

B. 62.5

C. 31.25

D. 625

Explanation:

349. Compute the speed of sound in neon gas at 27ยฐC of molecular mass 20.18 kg/kmol and k of 1.67.

A. 454 m/s

B. 564 m/s

C. 356 m/s

D. 434 m/s

Explanation:

350. A magnifying glass has a lens with an index of refraction 5.4 and radii of curvature of 2.95 feet and 4.27 feet for the two faces. What is the magnification of the lens when it is held 2.36 inches from an object being viewed?

A. 1.6

B. 2.78

C. 2.16

D. 1.98

Explanation:

#### Online Questions and Answers in Physics Series

Following is the list of practice exam test questions in this brand new series:

College Physics MCQs
PART 1: MCQ from Number 1 โ 50                        Answer key: PART 1
PART 2: MCQ from Number 51 โ 100                   Answer key: PART 2
PART 3: MCQ from Number 101 โ 150                 Answer key: PART 3
PART 4: MCQ from Number 151 โ 200                 Answer key: PART 4
PART 5: MCQ from Number 201 โ 250                 Answer key: PART 5
PART 6: MCQ from Number 251 โ 300                 Answer key: PART 6
PART 7: MCQ from Number 301 โ 350                 Answer key: PART 7
PART 8: MCQ from Number 351 โ 400                 Answer key: PART 8
PART 9: MCQ from Number 401 โ 450                 Answer key: PART 9
PART 10: MCQ from Number 451 โ 500                 Answer key: PART 10

Complete List of MCQs in General Engineering and Applied Science per topic

Series of MCQ in General Engineering and Applied Science

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