In A Raisin in the Sun, George suggest that Beneatha should be a certain type of girl and tells her to drop the "atmosphere". Elaborate what he implies by this.

In Lorraine Hansberry's A Raisin in the Sun, Beneatha dates the wealthy, well-educated man George Murchison; he is set up as a foil for Joseph Asagai, who also attracts her attention. In his pursuit of success, George has chosen to assimilate to white American culture, whereas Joseph is proud of his African heritage and teaches Beneatha about their shared culture and history. Joseph appreciates Beneatha's intellect and desire to learn, but George is not interested in Beneatha's mind, which he reveals when they come home from a date at the start of act 2, scene 2.
He tries to kiss her, and when Beneatha pulls away, they have the following exchange:

George: Look, we've had a nice evening; let's not spoil it, huh? . . .
He again turns her head and tries to nuzzle in and she turns away from him, not with distaste but with momentary lack of interest; in a mood to pursue what they were talking about.
Beneatha: I'm trying to talk to you.
George: We always talk.
Beneatha: Yes—and I love to talk.
George: Exasperated; rising I know it and I don't mind it sometimes . . . I want you to cut it out, see—The moody stuff, I mean. I don't like it. You're a nice-looking girl . . . all over. That's all you need, honey, forget the atmosphere. Guys aren't going to go for the atmosphere—they're going to go for what they see. Be glad for that. Drop the Garbo routine. It doesn't go with you. As for myself, I want a nice—Groping—simple Thoughtfully— sophisticated girl . . . not a poet—O.K.?

George shows a physical interest in Beneatha and her beauty, but he has little respect for who she is inside.
In scene 1 of act 2, Beneatha had remarked to her family that George was "shallow," and he only confirms her judgment here. The "atmosphere" he refers to consists essentially of her personality and intellect. She longs to have deep, serious discussions about the world, but George dismisses this as "moody" and unattractive. Beneatha finds this puzzling, since George is himself an educated man, but he reveals that the two of them have different ideas about the role of education:

George: I don't go out with you to discuss the nature of "quiet desperation" or to hear all about your thoughts—because the world will go on thinking what it thinks regardless—
Beneatha: Then why read books? Why go to school?
George: With artificial patience, counting on his fingers It's simple. You read books—to learn facts—to get grades—to pass the course—to get a degree. That's all —it has nothing to do with thoughts.

Upon realizing that George is—as she later tells Mama—"a fool," she ends their date.
This moment in the play underscores Beneatha's intelligence, determination, and authenticity. A man like George wants Beneatha to look good on his arm, treating her as an accessory to his wealth and image, but Beneatha values herself and her mind more than that.