The spectra of different elements can be distinguished because
a. they have the same spectral lines, but the lines are of different intensities.
b. they have spectral lines in different positions.
c. every element has one unique spectral line.
d. none of the above
b
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A convex lens has focal length f. An object is located at infinity. The image formed is located
A) at infinity. B) at 2f. C) between f and 2f. D) at f. E) between the lens and f.
Anne S. Moffat, in a paper in Science "Engineering plants to cope with metals" (Ref. 41) says: "Many plants cope with
metals by binding them in complexes with a class of peptides called phytochelatins and sequestering the complexes inside their cells. Now three groups have isolated genes for the enzymes, called phytochelatin synthases, that make the metal-binding peptides when the cell is exposed to toxic metals. ... After searching genome databases, they also found counterparts of the plant genes in the roundworm Caenorhabditis elegans." What are the implications of finding the same genes to inactivate metals in both plants and animals?
The isotope, tritium, has a half-life of 12.3 years. Assume we have 10 kg of the substance. What will be the disintegration constant (in s-1)?
a. 5.6 × 10^-2 b. 5.6 × 10^8 c. 3.2 × 10^7 d. 1.8 × 10^-9 e. 1.6 × 10^6
Matter Waves: Calculate the kinetic energy, in electron-volts, of a neutron that has a de Broglie wavelength of 7.2 × 10-12 m (mneutron = 1.675 × 10-27 kg, 1 eV = 1.6 × 10-19 J, h = 6.626 × 10-34 J ? s)
Fill in the blank(s) with the appropriate word(s).