物理

• A converging glass lens with a refractive index of 5 is placed in water with a refractive inde
• An object is located at 40 cm from the first of two thin converging lenses of focal lengths 20 c
• Two stars are separated by an angle of 3 × 10−5radians. What is the diameter of the smallest tel
• Unpolarized light of intensity I0is incident on a series of three polarizing filters. The axis o
• If a gas undergoes a series of pressure (P) and volume (V) changes, as shown below, how much wor
• There is a laminar flow in a tube. When both the radius and length of the tube are doubled, how
• A steam of water of density  ρ， cross-sectional area A, and speed υ strikes a wall that is perpe
• Water is flowing at 0 m/s in a circular pipe. If the diameter of the pipe decreases to 1/2 its
• A 0 nC point charge is embedded at the center of a nonconducting sphere (radius = 0 cm) whic
• A 0 A current flows along a wire with m. The wire resides in a uniform magnetic fieldT. The ma
• The current in an inductor (L = 40 mH) is described by with I in ampers and t in seconds. What
• A stiff wire bent into a semicircle of radius a = 0 cm is rotated at constant angular speed 40
• Three long wires parallel to the x axis carry currents as shown. If I = 20 A, what is the magnit
• The coil shown below has 2 turns, a cross-sectional area of 0.20 m2, and a field (parallel to th
• A series RLC circuit is connected to an ac source ( ). The resistance, capacitive reactance andi
• The rest mass of an electron is mo. What is the kinetic energy of an electron with the speed of
• In the hydrogen spectrum, the ratio of the wavelengths for Lyman-α radiation (n = 2 to n = 1) to
• A sample of radioactive nuclei of a certain element can decay only by γ -emission and β -emissio
• The radioactive isotope 226Ra  decays to 222 Rn with a half-life of 1600 years. The radioactive