optical microscopy

HESI A2

Biology HESI A2 Practice Test

1. Which of the following is true of optical microscopy?

A. Utilizes scanning electrons
B. Utilizes visible light
C. Utilizes dye for samples
D. More than one of the above is true

Correct answer: D

Rationale: The correct answer is D, 'More than one of the above is true.' Optical microscopy utilizes visible light (Choice B) and often involves the use of dyes for samples (Choice C). Using dyes helps enhance contrast, making it easier to visualize the structures being observed. Choice A is incorrect as optical microscopy does not utilize scanning electrons, but rather visible light.

2. What is the role of a catalyst in a chemical reaction?

A. Slows down the reaction
B. Has no effect
C. Speeds up the reaction
D. Stops the reaction

Correct answer: C

Rationale: A catalyst speeds up a chemical reaction by lowering the activation energy required for the reaction to occur. It does not get consumed in the reaction and remains unchanged at the end, allowing it to facilitate multiple reaction cycles. Choice A is incorrect because a catalyst actually speeds up the reaction. Choice B is incorrect because catalysts do have an effect by accelerating the reaction. Choice D is incorrect because catalysts do not stop the reaction, but rather increase the reaction rate.

3. What part of the eye is responsible for focusing light on the retina?

A. Cornea
B. Lens
C. Retina
D. Pupil

Correct answer: B

Rationale: The lens of the eye is responsible for focusing light on the retina. When light enters the eye, it first passes through the cornea, which helps in bending the light, and then the lens further refracts and focuses the light onto the retina at the back of the eye. The retina contains photoreceptor cells that convert light into neural signals, which are then sent to the brain for visual processing. The cornea is the transparent outermost layer of the eye that helps in focusing light, but the main responsibility lies with the lens. The retina is the layer at the back of the eye that receives the focused light and initiates the process of vision. The pupil is the opening in the center of the iris that controls the amount of light entering the eye and is not directly involved in focusing light on the retina.

4. Another word for UNDER OBSERVATION is?

A. Cognition
B. Isolation
C. Surveillance
D. Assessment

Correct answer: C

Rationale: Another word for UNDER OBSERVATION is surveillance. Surveillance refers to the close observation of a person, group, or place, especially in a secret or discreet manner. It involves monitoring and watching over someone or something closely for a specific purpose. Therefore, the word 'surveillance' is the most suitable synonym for under observation in this context. Choice A, 'Cognition,' refers to the mental process of acquiring knowledge and understanding through thoughts, experience, and the senses; it is not synonymous with under observation. Choice B, 'Isolation,' means the process or fact of isolating or being isolated, which does not convey the idea of close monitoring. Choice D, 'Assessment,' involves evaluating or judging the nature, ability, or quality of something, which is different from the act of observing closely.

5. Express the ratio of 6:7 as a percentage.

A. 67%
B. 76%
C. 86%
D. 93%

Correct answer: A

Rationale: To express the ratio 6:7 as a percentage, we first need to find the total parts in the ratio, which is 6 + 7 = 13. To convert this ratio to a percentage, divide the part you want to find the percentage for by the total parts, then multiply by 100. In this case, to find the percentage for 6 in the ratio 6:7, the calculation would be (6/13) * 100 = 46.15%. Therefore, the correct answer is A, 67%. Choices B, C, and D are incorrect percentages as they do not result from the correct calculation for the given ratio.