After focusing on an object with the low power objective lens, you are trying to bring it into focus under the 40x objective lens, but the field of view is very dark. Which of the following may remedy this problem?
Only use lower power magnification.
Add more immersion oil.
Adjust the fine adjustment knob.
Increase the light intensity.
The Correct Answer is D
Choice A rationale: Only use lower power magnification is incorrect because this does not solve the problem of the dark field of view, but rather avoids it. Using lower power magnification means that you will not be able to see the details of the specimen that you want to observe under the 40x objective lens. Lower power magnification also has a larger field of view and a lower resolution than higher power magnification.
Choice B rationale: Add more immersion oil is incorrect because immersion oil is only used for the highest magnification objective lens, which is the 100x oil immersion objective lens, not the 40x objective lens. Immersion oil is a type of oil that has the same refractive index as glass, which means that it bends light in the same way as glass. Immersion oil is applied between the slide and the lens to reduce the refraction of light and increase the clarity of the image.
Choice C rationale: Adjust the fine adjustment knob is incorrect because the fine adjustment knob is used to fine-tune the focus of the specimen, not the brightness of the field of view. The fine adjustment knob is a small knob that is located on the side of the microscope, next to the coarse adjustment knob. The fine adjustment knob is used to make small changes in the distance between the objective lens and the specimen, which improves the sharpness of the image.
Choice D rationale: Increase the light intensity is correct because the light intensity is the amount of light that reaches the specimen and the objective lens, which affects the brightness of the field of view. The light intensity can be adjusted by using the rheostat, which is a dial that is located on the base of the microscope, next to the light source. The rheostat can increase or decrease the voltage of the light source, which changes the brightness of the light. Increasing the light intensity can make the field of view brighter and easier to see.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale: The rate of diffusion is the speed at which particles move from an area of high concentration to an area of low concentration. This depends on the temperature, the size of the particles, and the medium they are in. Temperature affects the kinetic energy and the speed of the particles, which in turn affects the frequency and intensity of their collisions. Higher temperatures mean higher kinetic energy and faster particles, which leads to faster diffusion. ³
Choice B rationale: The change in rate of diffusion is not unaffected by temperature. Temperature is one of the main factors that influences the rate of diffusion, as explained above. Therefore, this choice is incorrect.
Choice C rationale: Diffusion does not halt when temperature is increased. On the contrary, diffusion becomes faster when temperature is increased, as explained above. Therefore, this choice is incorrect.
Choice D rationale: The change in rate of diffusion is not unpredictable when temperature is increased. There is a clear relationship between temperature and diffusion, as explained above. Therefore, this choice is incorrect.
Choice E rationale: The rate of diffusion does not decrease when temperature is increased. On the contrary, diffusion becomes faster when temperature is increased, as explained above. Therefore, this choice is incorrect..
Correct Answer is A
Explanation
Red blood cells are animal cells that lack a cell wall, a rigid structure that surrounds the cell membrane of plant cells, such as Elodea cells. A cell wall provides support and protection for the cell, and prevents excessive water uptake or loss. Red blood cells, on the other hand, rely on the osmotic balance of their environment to maintain their shape and function. If red blood cells are placed in a hypotonic solution, where the water concentration is higher outside than inside the cell, they will swell and burst due to osmosis. This is called hemolysis. If red blood cells are placed in a hypertonic solution, where the water concentration is lower outside than inside the cell, they will shrink and lose their ability to carry oxygen. This is called crenation.
Elodea cells, however, can withstand hypotonic or hypertonic solutions without bursting or shrinking, because their cell wall prevents the water from entering or leaving the cell beyond a certain point. Therefore, a major difference between red blood cells and Elodea cells is that Elodea cells have a cell wall, which protects them from bursting.
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