65. When the object distance is doubled, the focal length of the lens a) doubles b) halves c) quadruples d) decreases by 4 x e) remains the same 66. Which of the following is written in the correct order towards increasing frequency? a) radio, visible, microwave b) infrared, microwave, x ray c) radio, gamma, microwave d) infrared, visible, ultraviolet e) ultraviolet, infrared, gamma 67. The half-life of element X is 8 days. If 120 g of element X is placed on a table, how much remains after 24 days? a) 30 g b ) 15 g c) 10 g d) 24 g e) 5 g 68. 1.5x 10% molecules of sulfuric acid, H2SO4, would have a mass closest to a) 100g b) 50g c) 25g d) 10g e) 1.5g 69. Which group in the periodic table contains the alkali metals? a) IA b) IIA C) IIIA d) IVA e) VIIA 70. Ignoring air resistance, an object falling toward the surface of the earth has an acceleration that is a) constant. b) increasing. c) decreasing. d) zero e) dependent on the weight of the object. 71. Complete the following nuclear reaction: 194 77 Ir -> 4 24 0 + a) 182 70 Yb b) 186 52 Te c) 186 85 Tm d) 78 69 Tm e) 186 68 Er that is 72. Ignoring air resistance, an object falling toward the surface of the earth has a velocity a) constant. b) increasing. e) inversely proportional to its mass c) decreasing. d) acquired instantaneously