How does the fraction of oxygen in Earth's atmosphere today compare to what it was 3 billion years ago?
a. It has significantly declined.
b. It has significantly increased.
c. It kept increasing up to 2 billion years ago but has been declining ever since.
d. It hasn't changed.
b. It has significantly increased.
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A diatomic molecule has 2.6 × 10-5 eV of rotational energy in the l = 2 quantum state. What is its rotational energy in the l = 1 quantum state?
A) 7.8 µeV B) 8.7 µeV C) 5.3 µeV D) 4.1 µeV E) 3.4 µeV
Diffraction Gratings: A metallic sheet has a large number of parallel slits, 5.0 mm wide and 20 cm apart. This sheet is used as a diffraction grating for microwaves. A wide parallel beam of microwaves is incident normally on the sheet. If the intensity maxima occur 2.0° apart in the central region, what is the wavelength of the microwaves?
A. 5.0 mm B. 6.0 mm C. 7.0 mm D. 8.0 mm E. 9.0 mm
What is the total energy of a 300-g mass that is attached to a horizontal spring with a force constant of 260 N/m and oscillates along a frictionless horizontal surface with an amplitude of 8.0 cm?
A) 21 J B) 0.83 J C) 2.4 J D) 1.6 J E) 6.2 J
The current density magnitude 
