# Topics in Physics

1. A 500-microFarad capacitor is discharged through a 4.7-Mega ohm resistance. What is the time constant?

a. 600 s

b. 300 s

c. 2350 s

d. 1200 s

2. Water in a fish tank is 7.6 feet deep, and a coin rests on the bottom. How far below the surface does the coin appear to be when viewed from above? (Assume a small angle of incidence.)

a. 3.8 feet

b. 5.8 feet

c. 2.6 feet

d. 5.2 feet

3. A myopic person wears eyeglasses with a lens strength of - 5.0 diopters. Where is the far point for that person's eyes?

a. 3.5 m

b. 20 cm

c. 28.6 cm

d. infinity

4. Red light of wavelength 632.8 nm is incident on a pair of slits whose separation is 0.25mm. What is the separation of neighboring interference maxima on a screen 180cm from the slits?

a. 1.5 cm

b. 3.0 mm

c. 4.5 mm

d. 1.2 mm

5. The mean life of muons is 2.2 us. What is the mean life of a beam of muons moving at a speed of 0.945c relative to you?

a. 70 micro.s

b. 2.2 micro.s

c. 0.11 micro.s

d. 6.6 micro.s

6. A sample of Barium isotope has a half-life of 2.5 min and an intial activity of 10 x 10^6 Bq. What is its activity after 25 min have elapsed?

a. 9780 Bq

b. 4600 Bq

c. 19,600 Bq

d. 22,000 Bq

https://brainmass.com/physics/isotopes/topics-in-physics-30757

#### Solution Preview

1.)

capacitance C = 500-microFarad = 500*10^(-6) F

ResistanceR = 4.7-Mega ohm = 4.7*10^6 ohm

Therefore, time constant T = R*C = 4.7*500 =2350.0 sec --Answer (c)

2.)

depth D = 7.6 feet

apperent depth D' = D/mu = 7.6/1.33 = 5.8 ft --Answer ...

#### Solution Summary

The solution provides calculations for various physics problems. Topics covered include: resistance, angle of incidence, far point, interference between slits, muons, isotopes.