Blog

Refracting telescope: The objective and the eyepiece of a refracting astronomical telescope have focal lengths of 320 cm and 4.0 cm, respectively. The telescope is used to view Neptune and the final image is set at infinity. The diameter of Neptune is 4.96 × 107 m and the distance from the earth at the time of observation is 4.4 × 1012 m. What is the angle (in mrad) subtended by the final telescopic image of Neptune?

Field intensity: Near the earth the intensity of radiation from the sun is 1.35 kW/m2. What volume of space in this region contains 1.0 J of electromagnetic energy? (c = 3.0 × 108 m/s, μ0 = 4π × 10-7 T ∙ m/A, ε0 = 8.85 × 10-12 C2/N ∙ m2)

What value of resistor R gives the circuit in the figure above a time constant of 16

A 9.0 mH inductor is connected in parallel with a variable capacitor. The capacitor can be varied from 100 pF to 340 pF. a) What is the minimum oscillation frequency for this circuit? (2 points) b) What is the maximum oscillation frequency for this circuit?  (2 points)

A3.0 mH inductor is connected in parallel with a variable capacitor. The capacitor can be varied from 160 pF to 280 pF. a) What is the minimum oscillation frequency for this circuit? (2 points) b) What is the maximum oscillation frequency for this circuit?  (2 points)

Assume that a 7.0 cm diameter, 100 W light bulb radiates all its energy as a single wavelength of visible light. (

The figure shows a 30-cm-diameter loop in three different magnetic fields. The loop’s resistance is 0.23 

What is the electric field amplitude of an electromagnetic wave whose magnetic field amplitude is 1.80 mT?

A series RLC circuit attached to a 120 V/60 Hz power line draws 3.00 A of current with a power factor of 0.890. What is the value of the resistor?

For a science project, you would like to horizontally suspend an 8.5 by 11 inch sheet of black paper in a vertical beam of light whose dimensions exactly match the paper. If the mass of the sheet is 1.2 g, what light intensity will you need? (1 in = 2.54 cm)